<?xml version="1.0" encoding="utf-8"?>
                    <manifest
                        xmlns:android="http://schemas.android.com/apk/res/android"
                        android:versionCode="1"
                        android:versionName="1.0">
                    
                        <uses-feature android:name="android.hardware.sensor.compass"
                            android:required="true" />
                    
                        <application
                            android:allowBackup="true"
                            android:icon="@mipmap/ic_launcher"
                            android:roundIcon="@mipmap/ic_launcher_round"
                            android:label="@string/app_name"
                            android:supportsRtl="true"
                            android:theme="@style/AppTheme">
                    
                            <activity android:name=".MainActivity">
                                <intent-filter>
                                    <action android:name="android.intent.action.MAIN" />
                                    <category android:name="android.intent.category.LAUNCHER" />
                                </intent-filter>
                            </activity>
                            <activity
                                android:name=".DisplayMessageActivity"
                                android:parentActivityName=".MainActivity" />
                        </application>
                    </manifest>
            

                plugins {
                    id 'com.android.application'
                }
                android {
                    namespace 'com.example.appname'
                    compileSdk 32
                    defaultConfig {
                        applicationId "com.example.appname"
                        minSdk 25
                        targetSdk 32
                        versionCode 1
                        versionName "1.0"
                        testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
                    }
                    buildTypes {
                        release {
                            minifyEnabled false
                            proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
                        }
                    }
                    compileOptions {
                        sourceCompatibility JavaVersion.VERSION_1_8
                        targetCompatibility JavaVersion.VERSION_1_8
                    }
                }
                dependencies {
                    implementation 'androidx.appcompat:appcompat:1.5.1'
                    implementation 'com.google.android.material:material:1.7.0'
                    implementation 'androidx.constraintlayout:constraintlayout:2.1.4'
                    testImplementation 'junit:junit:4.13.2'
                    androidTestImplementation 'androidx.test.ext:junit:1.1.3'
                    androidTestImplementation 'androidx.test.espresso:espresso-core:3.4.0'
                }
            

                    public class MainActivity extends AppCompatActivity {
                        @Override
                        protected void onCreate(Bundle savedInstanceState) {
                            super.onCreate(savedInstanceState);
                            setContentView(R.layout.activity_main);
                        }
                    }
                

                public class MainActivity extends AppCompatActivity {
                    private static final String TAG = "debug_app";
                    @Override
                    protected void onCreate(Bundle savedInstanceState) {
                        super.onCreate(savedInstanceState);
                        setContentView(R.layout.activity_main);
                        Log.d(TAG, "onCreate:");
                    }
                    @Override
                    protected void onStart() {
                        super.onStart();
                        Log.d(TAG, "onStart: ");
                    }
                    @Override
                    protected void onResume() {
                        super.onResume();
                        Log.d(TAG, "onResume: ");
                    }
                    @Override
                    protected void onPause() {
                        super.onPause();
                        Log.d(TAG, "onPause: ");
                    }
                    @Override
                    protected void onStop() {
                        super.onStop();
                        Log.d(TAG, "onStop: ");
                    }
                    @Override
                    protected void onDestroy() {
                        super.onDestroy();
                        Log.d(TAG, "onDestroy: ");
                    }
                }
            

                public class FirstActivity extends Activity {
                }
            

                public class FirstActivity extends AppCompatActivity {
                    @Override
                    protected void onCreate(@Nullable Bundle savedInstanceState) {
                        super.onCreate(savedInstanceState);
                        setContentView(R.layout.activity_first);
                    }
                }
            

                <application
                       ... >
                    <activity android:name=".FirstActivity"
                        android:exported="true">
                        <intent-filter>
                            <action android:name="android.intent.action.MAIN" />
                            <category android:name="android.intent.category.LAUNCHER" />
                        </intent-filter>
                    </activity>
                </application>
            

                <application
                       ... >
                    <activity android:name=".FirstActivity"
                        android:exported="true">
                        <intent-filter>
                            <action android:name="android.intent.action.MAIN" />
                            <category android:name="android.intent.category.LAUNCHER" />
                        </intent-filter>
                    </activity>
                    <activity android:name=".SecondActivité"
                        android:exported="false"/>
                </application>
            

                public class MainActivity extends AppCompatActivity {
                    Context context;
                    @Override
                    protected void onCreate(Bundle savedInstanceState) {
                        super.onCreate(savedInstanceState);
                        context = this; //don t forget this line, else you will have NullPointer
                        setContentView(R.layout.activity_main);
                    }
                }
            

                    android:id="@+id/my_id"
                

                    <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
                            xmlns:app="http://schemas.android.com/apk/res-auto"
                            xmlns:tools="http://schemas.android.com/tools"
                            android:layout_width="match_parent"
                            android:layout_height="match_parent"
                            android:orientation="vertical"
                            tools:context=".MainActivity">
                        <TextView
                                android:layout_width="match_parent"
                                android:layout_height="wrap_content"
                                android:text="Hello World!" />
                        <TextView
                                android:layout_width="wrap_content"
                                android:layout_height="wrap_content"
                                android:layout_gravity="right"
                                android:text="Hello World!" />
                        <TextView
                                android:layout_width="match_parent"
                                android:gravity="right"
                                android:layout_height="wrap_content"
                                android:text="Hello World!" />
                        <TextView
                                android:layout_width="wrap_content"
                                android:layout_height="wrap_content"
                                android:layout_gravity="center"
                                android:text="Hello World!" />
                    </LinearLayout>
                

                    <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
                            xmlns:app="http://schemas.android.com/apk/res-auto"
                            xmlns:tools="http://schemas.android.com/tools"
                            android:layout_width="match_parent"
                            android:layout_height="match_parent"
                            android:orientation="vertical"
                            tools:context=".MainActivity">
                        <Button
                                android:layout_width="match_parent"
                                android:layout_height="0dp"
                                android:layout_weight="40"
                                android:text="btn 1" />
                        <Button
                                android:layout_width="match_parent"
                                android:layout_height="0dp"
                                android:layout_weight="60"
                                android:text="btn 2" />
                    </LinearLayout>
                

                    <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
                            xmlns:app="http://schemas.android.com/apk/res-auto"
                            xmlns:tools="http://schemas.android.com/tools"
                            android:layout_width="match_parent"
                            android:layout_height="match_parent"
                            android:orientation="horizontal"
                            tools:context=".MainActivity">
                        <Button
                                android:layout_width="0dp"
                                android:layout_height="match_parent"
                                android:layout_weight="2"
                                android:text="btn 1" />
                        <Button
                                android:layout_width="0dp"
                                android:layout_height="match_parent"
                                android:layout_weight="5"
                                android:text="btn 2" />
                    </LinearLayout>
                

                    public class MainActivity extends AppCompatActivity {
                        Context context;
                        @Override
                        protected void onCreate(Bundle savedInstanceState) {
                            super.onCreate(savedInstanceState);
                            context = this;
                            //set UI width XML File
                            setContentView(R.layout.activity_main); //we give here reference of XML file
                            
                            //set view width Java File
                            LinearLayout container = new LinearLayout(context);
                            setContentView(container);
                        }
                    }
                

                        <?xml version="1.0" encoding="utf-8"?>
                        <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
                                xmlns:app="http://schemas.android.com/apk/res-auto"
                                xmlns:tools="http://schemas.android.com/tools"
                                android:layout_width="match_parent"
                                android:layout_height="match_parent"
                                android:orientation="vertical"
                                tools:context=".MainActivity">
                            <TextView
                                    android:layout_width="wrap_content"
                                    android:layout_height="wrap_content"
                                    android:text="Hello World!" />
                        </LinearLayout>
                

                    public class MainActivity extends AppCompatActivity {
                        @Override
                        protected void onCreate(Bundle savedInstanceState) {
                            super.onCreate(savedInstanceState);
                            setContentView(R.layout.activity_main);
                        }
                    }
                

                TextView tv = new TextView(this);
                LinearLayout.LayoutParams params = new LinearLayout.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.WRAP_CONTENT);
                tv.setLayoutParams(params);
                

                    public class MainActivity extends AppCompatActivity {
                        Context context;
                        @Override
                        protected void onCreate(Bundle savedInstanceState) {
                            super.onCreate(savedInstanceState);
                            context = this;
                            //create instance of linear layout
                            LinearLayout linearLayoutMain = new LinearLayout(context);
                            linearLayoutMain.setLayoutParams(new LinearLayout.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.MATCH_PARENT));
                            linearLayoutMain.setOrientation(LinearLayout.VERTICAL);
                            //add linearLayout as main container of activity
                            setContentView(linearLayoutMain);
                            //create textview
                            TextView textView = new TextView(context);
                            textView.setText("Hello World!");
                            textView.setLayoutParams(new LinearLayout.LayoutParams(ViewGroup.LayoutParams.WRAP_CONTENT, ViewGroup.LayoutParams.WRAP_CONTENT));
                            //set text view as child of linearlayout
                            linearLayoutMain.addView(textView);
                        }
                    }
                

                    <?xml version="1.0" encoding="utf-8"?>
                    <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
                            xmlns:app="http://schemas.android.com/apk/res-auto"
                            xmlns:tools="http://schemas.android.com/tools"
                            android:layout_width="match_parent"
                            android:layout_height="match_parent"
                            android:orientation="vertical"
                            tools:context=".MainActivity">
                        <TextView
                                android:id="@+id/text_view"
                                android:layout_width="wrap_content"
                                android:layout_height="wrap_content"
                                android:text="Hello World!" />
                    </LinearLayout>
                

                    public class MainActivity extends AppCompatActivity {
                        Context context;
                        @Override
                        protected void onCreate(Bundle savedInstanceState) {
                            super.onCreate(savedInstanceState);
                            context = this;
                            setContentView(R.layout.activity_main);
                            //access to textview
                            TextView textView = findViewById(R.id.text_view);
                            //change value of textview
                            textView.setText("New text to print");
                        }
                    }
                

                    <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
                            android:layout_width="match_parent"
                            android:layout_height="match_parent"
                            android:orientation="horizontal"
                            android:padding="5dp">
                        <TextView
                                android:layout_width="0dp"
                                android:layout_height="wrap_content"
                                android:layout_weight="10"
                                android:background="#f00"
                                android:gravity="center"
                                android:textSize="20dp"
                                android:textColor="#fff"
                                android:text="Left" />
                        <TextView
                                android:layout_width="0dp"
                                android:layout_height="wrap_content"
                                android:layout_weight="10"
                                android:background="#0f0"
                                android:gravity="center"
                                android:textSize="20dp"
                                android:textColor="#fff"
                                android:text="Right" />
                        <TextView
                                android:id="@+id/tv_view_number"
                                android:layout_width="0dp"
                                android:layout_height="wrap_content"
                                android:layout_weight="10"
                                android:background="#00f"
                                android:gravity="center"
                                android:textSize="20dp"
                                android:textColor="#fff"
                                android:text="No " />
                    </LinearLayout>
                

                    public class InflatorActivity extends AppCompatActivity {
                        Context context;
                        @Override
                        protected void onCreate(Bundle savedInstanceState) {
                            super.onCreate(savedInstanceState);
                            context = this;
                            LinearLayout llMain = new LinearLayout(context);
                            llMain.setOrientation(LinearLayout.VERTICAL);
                            setContentView(llMain);
                            for (int i = 0; i < 10; i++) {
                                //deserialization of view
                                LinearLayout linearLayoutSmallView = (LinearLayout) LayoutInflater.from(context).inflate(R.layout.small_view,null);
                                TextView textViewNumberView = linearLayoutSmallView.findViewById(R.id.tv_view_number);
                                textViewNumberView.setText("No : " + (i+1));
                                llMain.addView(linearLayoutSmallView);
                            }
                        }
                    }
                

                Intent intent = new Intent(ctx,ClassName.class);
                startActivity(intent);
            

                            Intent intent = new Intent(this, SecondeActivity.class);
                            intent.putExtra("name","user name");
                            intent.putExtra("id", "456-fesdf-464sdf");
                            intent.putExtra("year", 27);
                            startActivity(intent);
                        

                            Intent intent = getIntent();
                            String nameValue = intent.getStringExtra("name");
                            String idValue = intent.getStringExtra("id");
                            int yearValue =  intent.getIntExtra("year", -1);
                        

                ActivityResultLauncher<Intent> resultActivity = registerForActivityResult(
                        new ActivityResultContracts.StartActivityForResult(),
                        new ActivityResultCallback<ActivityResult>() {
                            @Override
                            public void onActivityResult(ActivityResult result) {
                                if (result.getResultCode() == RESULT_OK) {
                                    //do instruction when result
                                    Intent intent = result.getData();
                                    String dataString = intent.getStringExtra("dataKey");
                                }
                            }
                        }
                );
                Intent intent = new Intent(this, SecondeActivity.class);
                resultActivity.launch(intent);
            

                button.setOnClickListener(new View.OnClickListener() {
                    @Override
                    public void onClick(View v) {
                        Intent intent = new Intent();
                        intent.putExtra("dataKey","hello data"); //1
                        setResult(RESULT_OK, intent); //2
                        finish(); //3
                    }
                });
            

                    MyProject/
                        src/
                            MyActivity.java
                        res/
                            drawable/
                                graphic.png
                            layout/
                                main.xml
                                info.xml
                            mipmap/
                                icon.png
                            values/
                                strings.xml
                

                    public class R {
                        public static class layout{
                            public static final int activity_main = 0xabc123;
                            public static final int my_layout = 0xabc124;
                            public static final int other_layout = 0xabc125;
                        }
                        public static class drawable{
                            public static final int image1 = 0xbcd123;
                            public static final int image2 = 0xbcd124;
                            public static final int chat = 0xbcd125;
                        }
                        public static class string{
                            public static final int msg_welcom = 0xefa123;
                            public static final int app_name = 0xefa124;
                            public static final int msg_btn_send = 0xefa125;
                        }
                        public static class color{
                            public static final int color_texte = 0x456fa12;
                            public static final int color_btn = 0x456fa13;
                            public static final int color_border = 0x456fa14;
                            public static final int color_title = 0x456fa15;
                        }
                    }
                

                    Resources resources = context.getResources();
                    String stringRessource = resources.getString(R.string.key_ressource);
                    
                    //XXX resValue = resources.getXXX(id);
                

                    @[package:]type_ressource/nom_ressource
                

                    @+[package:]type/nom
                

                    <string name="dyn1">Hello %1$s, you have %2$d years</string>
                

                    Resources res = context.getResources();
                    String chaine = res.getString(R.string.dyn1, "durand", 32);
                

                    AssetManager assetManager = getAssets(); //into activity
                    AssetManager assetManager = context.getAssets(); // everywhere in application
                    try {
                        InputStream inputStream = assetManager.open("fileName");
                    } catch (IOException e) {
                        throw new RuntimeException(e);
                    }
                

                    InputStream inputStream = assetManager.open("fileName");
                    Drawable drawableImage = Drawable.createFromStream(inputStream, null);
                    Bitmap bitmapImage = BitmapFactory.decodeStream(inputStream);
                

                                <menu xmlns:android="http://schemas.android.com/apk/res/android"
                                    xmlns:app="http://schemas.android.com/apk/res-auto">
                                <item
                                        android:id="@+id/menu_play"
                                        android:icon="@android:drawable/ic_media_play"
                                        android:title="play"
                                        app:showAsAction="always" />
                                <item
                                        android:id="@+id/menu_stop"
                                        android:icon="@android:drawable/ic_media_stop"
                                        android:title="stop"
                                        app:showAsAction="always" />
                                <item
                                        android:id="@+id/menu_next"
                                        android:title="next"
                                        app:showAsAction="always" />
                                <item
                                        android:id="@+id/menu_pause"
                                        android:icon="@android:drawable/ic_media_pause"
                                        android:title="pause"
                                        app:showAsAction="ifRoom" />
                                <item
                                        android:id="@+id/menu_reset"
                                        android:title="reset"
                                        app:showAsAction="never" />
                            </menu>
                            

                @Override
                public boolean onCreateOptionsMenu(Menu menu) {
                    MenuInflater menuInflater = getMenuInflater();
                    menuInflater.inflate(R.menu.layout_menu, menu);
                    return true;
                }
            

                @Override
                public boolean onCreateOptionsMenu(Menu menu) {
                    int idItem = 1;        // exemple pour ajouter un item
                    int order = 1;
                    MenuItem menuItem = menu.add(0, idItem, order, "mon menu");
                    return true;
                }
            

                @Override
                public boolean onOptionsItemSelected(@NonNull MenuItem item) {
                    boolean retour = super.onOptionsItemSelected(item);
                    switch (item.getItemId()) {
                        case R.id.menu_play:
                            //action todo
                            retour = true;
                            break;
                        case R.id.menu_stop:
                            //action todo
                            retour = true;
                            break;
                        case R.id.menu_pause:
                            //action todo
                            retour = true;
                            break;
                        case R.id.menu_next:
                            //action todo
                            retour = true;
                            break;
                        case R.id.menu_reset:
                            //action todo
                            retour = true;
                            break;
                    }
                    return retour;
                }
            

                AlertDialog.Builder builder = new AlertDialog.Builder(context);
                builder.setTitle("my wonderful title");
                builder.setMessage("my beautiful Message to print ");
                AlertDialog dialog = builder.create();
                dialog.show();
                //or
                AlertDialog dialog = builder.show();
            

                AlertDialog.Builder builder = new AlertDialog.Builder(context);
                builder.setTitle("my wonderful title");
                builder.setMessage("my beautiful Message to print ");
                builder.setPositiveButton("Yes", new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialog, int which) {
                        //action if yes is select
                    }
                });
                builder.setNeutralButton("i don't know", new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialog, int which) {
                        //action if i don't know is select
                    }
                });
                builder.setPositiveButton("no", new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialog, int which) {
                        //action if no select
                    }
                });
                AlertDialog dialog = builder.show();
            

                String[] items = new String[]{"orange","blue","green"};
                AlertDialog.Builder builder = new AlertDialog.Builder(context);
                builder.setTitle("my wonderful title");
                builder.setItems(items, new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialog, int which) {
                        String value = items[which];//which = position of item select
                    }
                });
                AlertDialog dialog = builder.show();
            

                <string-array name="colors_list">
                    <item>orange</item>
                    <item>blue</item>
                    <item>green</item>
                </string-array>
            

                builder.setItems(R.array.colors_list, new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialog, int which) {
                        String[] items = getResources().getStringArray(R.array.colors_list); //pour récupérer les données depuis le répertoire Ressource
                        String value = items[which];//which = position of item select
                    }
                });
            

vue définie en xml

                <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
                        android:layout_width="match_parent"
                        android:layout_height="match_parent"
                        android:orientation="vertical">
                    <LinearLayout
                            android:layout_width="match_parent"
                            android:layout_height="wrap_content"
                            android:orientation="horizontal">
                        <TextView
                                android:layout_width="0px"
                                android:layout_height="wrap_content"
                                android:layout_weight="30"
                                android:text="login : " />
                        <EditText
                                android:id="@+id/ed_login_ad"
                                android:layout_width="0px"
                                android:layout_height="wrap_content"
                                android:layout_weight="70" />
                    </LinearLayout>
                    <LinearLayout
                            android:layout_width="match_parent"
                            android:layout_height="wrap_content"
                            android:orientation="horizontal">
                        <TextView
                                android:layout_width="0px"
                                android:layout_height="wrap_content"
                                android:layout_weight="30"
                                android:text="password : " />
                        <EditText
                                android:id="@+id/ed_password_ad"
                                android:layout_width="0px"
                                android:layout_height="wrap_content"
                                android:layout_weight="70" />
                    </LinearLayout>
                </LinearLayout>
            

code java pour un alert dialog avec une vue perso

                AlertDialog.Builder builder = new AlertDialog.Builder(context);
                builder.setTitle("my wonderful title");
                View view = LayoutInflater.from(context).inflate(R.layout.alert_dialog_layout,null);
                builder.setView(view);
                AlertDialog dialog = builder.show();
                

                EditText edLogin = view.findViewById(R.id.ed_login_ad);
            

                builder.setPositiveButton("Yes", new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialog, int which) {
                        AlertDialog alertDialog = (AlertDialog) dialog;
                        EditText edLogin = alertDialog.findViewById(R.id.ed_login_ad);
                    }
                });
            

                    view.setOnClickListener(new View.OnClickListener() {
                        @Override
                        public void onClick(View v) {
                            //action to do
                            v.setBackgroundColor(Color.GREEN);
                        }
                    });
                

                    view.setOnLongClickListener(new View.OnLongClickListener() {
                        @Override
                        public boolean onLongClick(View v) {
                            return true;
                        }
                    });
                

                    view.setOnFocusChangeListener(new View.OnFocusChangeListener() {
                        @Override
                        public void onFocusChange(View v, boolean hasFocus) {
                            if(hasFocus){
                                v.setBackgroundColor(Color.GREEN);
                            }else{
                                v.setBackgroundColor(Color.BLUE);
                            }
                        }
                    });
                

                    editText.addTextChangedListener(new TextWatcher() {
                        @Override
                        public void beforeTextChanged(CharSequence s, int start, int count, int after) {
                        }
                        @Override
                        public void onTextChanged(CharSequence s, int start, int before, int count) {
                        }
                        @Override
                        public void afterTextChanged(Editable s) {
                        }
                    });
                

                    radioButton.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {
                        @Override
                        public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
                        }
                    });
                

                    public class MainActivity extends AppCompactActivity {
                    ...
                    // exemple pour une activité, mais même approche pour une sous classe de View
                    @Override
                    public boolean onTouchEvent(MotionEvent event){
                    
                        int action = MotionEventCompat.getActionMasked(event);
                    
                        switch(action) {
                            case (MotionEvent.ACTION_DOWN) :
                                Log.d(DEBUG_TAG,"Action was DOWN");
                                return true;
                            case (MotionEvent.ACTION_MOVE) :
                                Log.d(DEBUG_TAG,"Action was MOVE");
                                return true;
                            case (MotionEvent.ACTION_UP) :
                                Log.d(DEBUG_TAG,"Action was UP");
                                return true;
                            case (MotionEvent.ACTION_OUTSIDE) :
                                Log.d(DEBUG_TAG,"Movement occurred outside bounds " +
                                        "of current screen element");
                                return true;
                            default :
                                return super.onTouchEvent(event);
                        }
                    }
                    
                    //exemple sur une sous-classe de View
                    View myView = findViewById(R.id.my_view);
                    myView.setOnTouchListener(new OnTouchListener() {
                        public boolean onTouch(View v, MotionEvent event) {
                            //action to do
                            return true;
                        }
                    });
                    
                

                    @Override
                    public boolean onTouchEvent(MotionEvent event) {
                        float xPosition = 0;
                        float yPosition = 0;
                        if(event.getActionMasked() == MotionEvent.ACTION_DOWN){
                            xPosition = event.getX();
                            yPosition = event.getY();
                        }
                        if(event.getActionMasked() == MotionEvent.ACTION_MOVE){
                            xPosition = event.getX();
                            yPosition = event.getY();
                        }
                        return super.onTouchEvent(event);
                    }
                

                    @Override
                    public boolean onTouchEvent(MotionEvent event) {
                        // get pointer index from the event object
                        int pointerIndex = event.getActionIndex();
                        // get pointer ID from pointerIndex
                        int pointerId = event.getPointerId(pointerIndex);
                        // get action
                        int maskedAction = event.getActionMasked();
                        switch (maskedAction) {
                            case MotionEvent.ACTION_DOWN:
                                Log.d(TAG, "index down: " + pointerId);
                                break;
                            case MotionEvent.ACTION_POINTER_DOWN: {
                                Log.d(TAG, "index down: " + pointerId);
                                break;
                            }
                            case MotionEvent.ACTION_MOVE: { // a pointer was moved
                                Log.d(TAG, "index move: " + pointerId);
                                break;
                            }
                            case MotionEvent.ACTION_UP:
                                Log.d(TAG, "index up: " + pointerId);
                
                                break;
                            case MotionEvent.ACTION_POINTER_UP:
                                Log.d(TAG, "index up: " + pointerId);
                                break;
                        }
                
                        return true;
                    }
                

                            public class EventActivity extends AppCompatActivity implements GestureDetector.OnGestureListener {
                                Context context;
                                @Override
                                protected void onCreate(Bundle savedInstanceState) {
                                    super.onCreate(savedInstanceState);
                                    context = this;
                                    setContentView(R.layout.activity_event);
                                }
                                @Override
                                public boolean onDown(MotionEvent e) {
                                    return false;
                                }
                                @Override
                                public void onShowPress(MotionEvent e) {
                                }
                                @Override
                                public boolean onSingleTapUp(MotionEvent e) {
                                    return false;
                                }
                                @Override
                                public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY) {
                                    return false;
                                }
                                @Override
                                public void onLongPress(MotionEvent e) {
                                }
                                @Override
                                public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY) {
                                    return false;
                                }
                            }
                        

                    public class EventActivity extends AppCompatActivity implements GestureDetector.OnGestureListener {
                        private String TAG = "debug-app";
                        GestureDetector gestureDetector;
                        Context context;
                        @Override
                        protected void onCreate(Bundle savedInstanceState) {
                            super.onCreate(savedInstanceState);
                            context = this;
                            setContentView(R.layout.activity_event);
                            gestureDetector = new GestureDetector(this,this);
                        }
                        @Override
                        public boolean onDown(MotionEvent e) {
                            return false;
                        }
                        @Override
                        public void onShowPress(MotionEvent e) {
                        }
                        @Override
                        public boolean onSingleTapUp(MotionEvent e) {
                            return false;
                        }
                        @Override
                        public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY) {
                            return false;
                        }
                        @Override
                        public void onLongPress(MotionEvent e) {
                        }
                        @Override
                        public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY) {
                            return false;
                        }
                    }
                

                    public class EventActivity extends AppCompatActivity implements GestureDetector.OnGestureListener {
                        private String TAG = "debug-app";
                        GestureDetector gestureDetector;
                        Context context;
                        @Override
                        protected void onCreate(Bundle savedInstanceState) {
                            super.onCreate(savedInstanceState);
                            context = this;
                            setContentView(R.layout.activity_event);
                            gestureDetector = new GestureDetector(this,this);
                        }
                        @Override
                        public boolean onTouchEvent(MotionEvent event) {
                            gestureDetector.onTouchEvent(event);
                            return true;
                        }
                        @Override
                        public boolean onDown(MotionEvent e) {
                            return false;
                        }
                        @Override
                        public void onShowPress(MotionEvent e) {
                        }
                        @Override
                        public boolean onSingleTapUp(MotionEvent e) {
                            return false;
                        }
                        @Override
                        public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY) {
                            return false;
                        }
                        @Override
                        public void onLongPress(MotionEvent e) {
                        }
                        @Override
                        public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY) {
                            return false;
                        }
                    }
                

                //si pas besoin de catégoriser les informations
                SharedPreferences sharedPreferences = PreferenceManager.getDefaultSharedPreferences(this);
                //si besoin de catégoriser
                SharedPreferences sharedPreferencesUser = context.getSharedPreferences("user", Context.MODE_PRIVATE);
            

                SharedPreferences sharedPreferences = PreferenceManager.getDefaultSharedPreferences(this);
                String guid = sharedPreferences.getString("id",null);
                int age = sharedPreferences.getInt("age",-1);
            

                SharedPreferences sharedPreferences = PreferenceManager.getDefaultSharedPreferences(this);
                SharedPreferences.Editor editor = sharedPreferences.edit();
                editor.putString("userName", "John Doe");
                editor.putFloat("xPosition", 42.56f);
                editor.putFloat("yPosition", 1056.89f);
                editor.apply();
            

                SharedPreferences sharedPreferences = PreferenceManager.getDefaultSharedPreferences(this);
                SharedPreferences.Editor editor = sharedPreferences.edit();
               
                //suppression par clef
                editor.remove("userName");
                editor.remove("id");
                editor.apply();
               
                //suppression total
                editor.clear();
                editor.apply();
            

            File file = new File(context.getFilesDir(), filename);
            

                String filename = "myFile.txt";
                String fileContents = "Hello world!";
                try (FileOutputStream fos = context.openFileOutput(filename, Context.MODE_PRIVATE)) {
                    fos.write(fileContents.toByteArray());
                }
            

                FileInputStream fileInputStream = context.openFileInput(fileName);
                InputStreamReader inputStreamReader =
                        new InputStreamReader(fileInputStream, StandardCharsets.UTF_8);
                StringBuilder stringBuilder = new StringBuilder();
                try (BufferedReader reader = new BufferedReader(inputStreamReader)) {
                    String line = reader.readLine();
                    while (line != null) {
                        stringBuilder.append(line).append('\n');
                        line = reader.readLine();
                    }
                } catch (IOException e) {
                    // Error occurred when opening raw file for reading.
                } finally {
                    String contents = stringBuilder.toString();
                }
            

                <uses-permission android:name="android.permission.MANAGE_EXTERNAL_STORAGE" />
            

                    File file = new File(Environment.getExternalStorageDirectory().getPath()+ File.separator+ "Android/data"+File.separator + getPackageName() + "/files/"+"myFile.txt" );
                

                CREATE TABLE etudiant (
                    id INTEGER PRIMARY KEY AUTOINCREMENT,
                    first_name TEXT,
                    last_name TEXT,
                    age
                );
            

                public class DataBaseHelper extends SQLiteOpenHelper {
                    public DataBaseHelper(@Nullable Context context, @Nullable String name, @Nullable SQLiteDatabase.CursorFactory factory, int version) {
                        super(context, name, factory, version);
                    }
                    @Override
                    public void onCreate(SQLiteDatabase db) {
                    }
                    @Override
                    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
                    }
                }
            

                @Override
                public void onCreate(SQLiteDatabase db) {
                    db.execSQL("CREATE TABLE etudiant (\n" +
                            "id INTEGER PRIMARY KEY AUTOINCREMENT," +
                            "first_name TEXT," +
                            "last_name TEXT," +
                            "age" +
                            ");");
                    db.execSQL("INSERT INTO etudiant ('first_name','last_name','age') values ('john','doe', 27), ('foo','bar',99);");
                }
                @Override
                public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
                    db.execSQL("DROP TABLE IF EXISTS etudiant");
                    onCreate(db);
                }
            

                public class ConnectionDB {
                    private static int version = 1;
                    private static String bnName = "myBd.db";
                    private static SQLiteDatabase bd = null;
                    private static DataBaseHelper helper;
                    
                    public static SQLiteDatabase getBd(Context context){
                        if(helper == null){
                            helper = new DataBaseHelper(context, bnName, null, version);
                        }
                        bd = helper.getWritableDatabase();
                        return bd;
                    }
                    public static void close(){
                        if(bd!= null &&  !bd.isOpen()){
                            bd.close();
                        }
                    }
                }
            

                    public class EtudiantManager {
                    
                        public static long add(Context context, Etudiant etudiantToAdd){
                            ContentValues contentValues = new ContentValues();
                            contentValues.put("first_name", etudiantToAdd.getFirstName());
                            contentValues.put("last_name", etudiantToAdd.getLastName());
                            contentValues.put("age", etudiantToAdd.getAge());
                            SQLiteDatabase bd = ConnectionDB.getBd(context); //on réutilise ConnctionDB ici
                            return bd.insert("etudiant", null, contentValues);
                        }
                    }
                

                public static void delete(Context context, int idEtudiant){
                    SQLiteDatabase bd = ConnectionDB.getBd(context);
                    bd.delete("etudiant","id = ?" , new String[]{String.valueOf(idEtudiant)});
                }
            

                public int delete (String table,
                                    String whereClause,
                                    String[] whereArgs)
            

                DELETE FROM etudiant WHERE id = ?
            

                DELETE FROM etudiant WHERE id = 7
            

                    DELETE FROM etudiant WHERE id = ? AND name LIKE ?
                

                    public static void update(Context context, Etudiant etudiantToUpdate) {
                        ContentValues contentValues = new ContentValues();
                        contentValues.put("first_name", etudiantToUpdate.getFirstName());
                        contentValues.put("age", etudiantToUpdate.getAge());
                        SQLiteDatabase bd = ConnectionDB.getBd(context);
                        long nbRowChange = bd.update("etudiant", contentValues, "id = ?", new String[]{String.valueOf(etudiantToUpdate.getId())});
                    }
                

                    public static ArrayList<Etudiant> getAll(Context context) {
                        SQLiteDatabase bd = ConnectionDB.getBd(context);
                        String query = "SELECT * FROM etudiant";
                        ArrayList<Etudiant> etudiants = null;
                        Cursor cursor = bd.rawQuery(query, null);
                        if (cursor.isBeforeFirst()) {
                            etudiants = new ArrayList<>();
                            while (cursor.moveToNext()) {
                                Etudiant etudiant = new Etudiant();
                                etudiant.setId(cursor.getInt(cursor.getColumnIndexOrThrow("id")));
                                etudiant.setFirstName(cursor.getString(cursor.getColumnIndexOrThrow("first_name")));
                                etudiant.setLastName(cursor.getString(cursor.getColumnIndexOrThrow("last_name")));
                                etudiant.setAge(cursor.getInt(cursor.getColumnIndexOrThrow("age")));
                                etudiants.add(etudiant);
                            }
                        }
                        return etudiants;
                    }
                

                public static ArrayList<Etudiant> getByAgeLimite(Context context, int ageLimite) {
                    SQLiteDatabase bd = ConnectionDB.getBd(context);
                    String query = "SELECT * FROM etudiant where age > ?";
                    ArrayList<Etudiant> etudiants = null;
                    Cursor cursor = bd.rawQuery(query, new String[]{String.valueOf(ageLimite)});
                    if (cursor.isBeforeFirst()) {
                        etudiants = new ArrayList<>();
                        while (cursor.moveToNext()) {
                            Etudiant etudiant = new Etudiant();
                            etudiant.setId(cursor.getInt(cursor.getColumnIndexOrThrow("id")));
                            etudiant.setFirstName(cursor.getString(cursor.getColumnIndexOrThrow("first_name")));
                            etudiant.setLastName(cursor.getString(cursor.getColumnIndexOrThrow("last_name")));
                            etudiant.setAge(cursor.getInt(cursor.getColumnIndexOrThrow("age")));
                            etudiants.add(etudiant);
                        }
                    }
                    return etudiants;
                }
                

                    SensorManager sensorManager = (SensorManager) getSystemService(Context.SENSOR_SERVICE);
                

                    List<Sensor> sensors = sensorManager.getSensorList(Sensor.TYPE_ALL);
                    for (Sensor sensor : sensors) {
                        Log.d("debug_app", "sensor: " + sensor.getName());
                        Log.d("debug_app", "sensor: " + sensor.getMinDelay());
                        Log.d("debug_app", "sensor: " + sensor.getVersion());
                        Log.d("debug_app", "sensor: " + sensor.getMaximumRange());
                    }
                

                    Sensor sensorLight = sensorManager.getDefaultSensor(Sensor.TYPE_LIGHT);
                    if(sensorLight != null){
                        // sensor existe
                    } else {
                        // prévenir l'utilisateur qu'on ne peut pas continuer
                    }
                

                SensorEventListener sensorEventListener = new SensorEventListener() {
                    @Override
                    public void onSensorChanged(SensorEvent event) {
                    }
                    @Override
                    public void onAccuracyChanged(Sensor sensor, int accuracy) {
                    }
                };
                

                    @Override
                    protected void onResume() {
                        super.onResume();
                        sensorManager.registerListener(sensorEventListener, sensorLight, SensorManager.SENSOR_DELAY_FASTEST);
                    }
                

                    @Override
                    protected void onPause() {
                        super.onPause();
                        sensorManager.unregisterListener(sensorEventListener,sensorLight);
                    }
                

                    public class SensorActivity extends AppCompatActivity {
                        TextView textView;
                        SensorManager sensorManager;
                        SensorEventListener sensorEventListener;
                        Sensor sensorLight;
                        @Override
                        protected void onCreate(Bundle savedInstanceState) {
                            super.onCreate(savedInstanceState);
                            setContentView(R.layout.activity_sensor);
                            textView = findViewById(R.id.text);
                            sensorManager = (SensorManager) getSystemService(Context.SENSOR_SERVICE);
                            sensorLight = sensorManager.getDefaultSensor(Sensor.TYPE_LIGHT);
                            sensorEventListener = new SensorEventListener() {
                                @Override
                                public void onSensorChanged(SensorEvent event) {
                                    float luxValue = event.values[0];
                                    textView.setText(String.valueOf(luxValue) + " lux");
                                }
                                @Override
                                public void onAccuracyChanged(Sensor sensor, int accuracy) {
                                }
                            };
                        }
                        @Override
                        protected void onResume() {
                            super.onResume();
                            sensorManager.registerListener(sensorEventListener, sensorLight, SensorManager.SENSOR_DELAY_FASTEST);
                        }
                        @Override
                        protected void onPause() {
                            super.onPause();
                            sensorManager.unregisterListener(sensorEventListener,sensorLight);
                        }
                    }
                

                    <uses-feature android:name="android.hardware.sensor.accelerometer"
                                  android:required="true" />
                

                    <?xml version="1.0" encoding="utf-8"?>
                    <manifest
                        xmlns:android="http://schemas.android.com/apk/res/android"
                        android:versionCode="1"
                        android:versionName="1.0">
                    
                        <uses-feature android:name="android.hardware.sensor.compass"
                            android:required="true" />
                    
                        <application
                            android:allowBackup="true"
                            android:icon="@mipmap/ic_launcher"
                            android:roundIcon="@mipmap/ic_launcher_round"
                            android:label="@string/app_name"
                            android:supportsRtl="true"
                            android:theme="@style/AppTheme">
                    
                            <activity android:name=".MainActivity">
                                <intent-filter>
                                    <action android:name="android.intent.action.MAIN" />
                                    <category android:name="android.intent.category.LAUNCHER" />
                                </intent-filter>
                            </activity>
                            <activity
                                android:name=".DisplayMessageActivity"
                                android:parentActivityName=".MainActivity" />
                        </application>
                    </manifest>
            

                plugins {
                    id 'com.android.application'
                }
                android {
                    namespace 'com.example.appname'
                    compileSdk 32
                    defaultConfig {
                        applicationId "com.example.appname"
                        minSdk 25
                        targetSdk 32
                        versionCode 1
                        versionName "1.0"
                        testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
                    }
                    buildTypes {
                        release {
                            minifyEnabled false
                            proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
                        }
                    }
                    compileOptions {
                        sourceCompatibility JavaVersion.VERSION_1_8
                        targetCompatibility JavaVersion.VERSION_1_8
                    }
                }
                dependencies {
                    implementation 'androidx.appcompat:appcompat:1.5.1'
                    implementation 'com.google.android.material:material:1.7.0'
                    implementation 'androidx.constraintlayout:constraintlayout:2.1.4'
                    testImplementation 'junit:junit:4.13.2'
                    androidTestImplementation 'androidx.test.ext:junit:1.1.3'
                    androidTestImplementation 'androidx.test.espresso:espresso-core:3.4.0'
                }
            

                    public class MainActivity extends AppCompatActivity {
                        @Override
                        protected void onCreate(Bundle savedInstanceState) {
                            super.onCreate(savedInstanceState);
                            setContentView(R.layout.activity_main);
                        }
                    }
                

                public class MainActivity extends AppCompatActivity {
                    private static final String TAG = "debug_app";
                    @Override
                    protected void onCreate(Bundle savedInstanceState) {
                        super.onCreate(savedInstanceState);
                        setContentView(R.layout.activity_main);
                        Log.d(TAG, "onCreate:");
                    }
                    @Override
                    protected void onStart() {
                        super.onStart();
                        Log.d(TAG, "onStart: ");
                    }
                    @Override
                    protected void onResume() {
                        super.onResume();
                        Log.d(TAG, "onResume: ");
                    }
                    @Override
                    protected void onPause() {
                        super.onPause();
                        Log.d(TAG, "onPause: ");
                    }
                    @Override
                    protected void onStop() {
                        super.onStop();
                        Log.d(TAG, "onStop: ");
                    }
                    @Override
                    protected void onDestroy() {
                        super.onDestroy();
                        Log.d(TAG, "onDestroy: ");
                    }
                }
            

                public class FirstActivity extends Activity {
                }
            

                public class FirstActivity extends AppCompatActivity {
                    @Override
                    protected void onCreate(@Nullable Bundle savedInstanceState) {
                        super.onCreate(savedInstanceState);
                        setContentView(R.layout.activity_first);
                    }
                }
            

                <application
                       ... >
                    <activity android:name=".FirstActivity"
                        android:exported="true">
                        <intent-filter>
                            <action android:name="android.intent.action.MAIN" />
                            <category android:name="android.intent.category.LAUNCHER" />
                        </intent-filter>
                    </activity>
                </application>
            

                <application
                       ... >
                    <activity android:name=".FirstActivity"
                        android:exported="true">
                        <intent-filter>
                            <action android:name="android.intent.action.MAIN" />
                            <category android:name="android.intent.category.LAUNCHER" />
                        </intent-filter>
                    </activity>
                    <activity android:name=".SecondActivité"
                        android:exported="false"/>
                </application>
            

                public class MainActivity extends AppCompatActivity {
                    Context context;
                    @Override
                    protected void onCreate(Bundle savedInstanceState) {
                        super.onCreate(savedInstanceState);
                        context = this; //don t forget this line, else you will have NullPointer
                        setContentView(R.layout.activity_main);
                    }
                }
            

                    android:id="@+id/my_id"
                

                    <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
                            xmlns:app="http://schemas.android.com/apk/res-auto"
                            xmlns:tools="http://schemas.android.com/tools"
                            android:layout_width="match_parent"
                            android:layout_height="match_parent"
                            android:orientation="vertical"
                            tools:context=".MainActivity">
                        <TextView
                                android:layout_width="match_parent"
                                android:layout_height="wrap_content"
                                android:text="Hello World!" />
                        <TextView
                                android:layout_width="wrap_content"
                                android:layout_height="wrap_content"
                                android:layout_gravity="right"
                                android:text="Hello World!" />
                        <TextView
                                android:layout_width="match_parent"
                                android:gravity="right"
                                android:layout_height="wrap_content"
                                android:text="Hello World!" />
                        <TextView
                                android:layout_width="wrap_content"
                                android:layout_height="wrap_content"
                                android:layout_gravity="center"
                                android:text="Hello World!" />
                    </LinearLayout>
                

                    <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
                            xmlns:app="http://schemas.android.com/apk/res-auto"
                            xmlns:tools="http://schemas.android.com/tools"
                            android:layout_width="match_parent"
                            android:layout_height="match_parent"
                            android:orientation="vertical"
                            tools:context=".MainActivity">
                        <Button
                                android:layout_width="match_parent"
                                android:layout_height="0dp"
                                android:layout_weight="40"
                                android:text="btn 1" />
                        <Button
                                android:layout_width="match_parent"
                                android:layout_height="0dp"
                                android:layout_weight="60"
                                android:text="btn 2" />
                    </LinearLayout>
                

                    <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
                            xmlns:app="http://schemas.android.com/apk/res-auto"
                            xmlns:tools="http://schemas.android.com/tools"
                            android:layout_width="match_parent"
                            android:layout_height="match_parent"
                            android:orientation="horizontal"
                            tools:context=".MainActivity">
                        <Button
                                android:layout_width="0dp"
                                android:layout_height="match_parent"
                                android:layout_weight="2"
                                android:text="btn 1" />
                        <Button
                                android:layout_width="0dp"
                                android:layout_height="match_parent"
                                android:layout_weight="5"
                                android:text="btn 2" />
                    </LinearLayout>
                

                    public class MainActivity extends AppCompatActivity {
                        Context context;
                        @Override
                        protected void onCreate(Bundle savedInstanceState) {
                            super.onCreate(savedInstanceState);
                            context = this;
                            //set UI width XML File
                            setContentView(R.layout.activity_main); //we give here reference of XML file
                            
                            //set view width Java File
                            LinearLayout container = new LinearLayout(context);
                            setContentView(container);
                        }
                    }
                

                        <?xml version="1.0" encoding="utf-8"?>
                        <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
                                xmlns:app="http://schemas.android.com/apk/res-auto"
                                xmlns:tools="http://schemas.android.com/tools"
                                android:layout_width="match_parent"
                                android:layout_height="match_parent"
                                android:orientation="vertical"
                                tools:context=".MainActivity">
                            <TextView
                                    android:layout_width="wrap_content"
                                    android:layout_height="wrap_content"
                                    android:text="Hello World!" />
                        </LinearLayout>
                

                    public class MainActivity extends AppCompatActivity {
                        @Override
                        protected void onCreate(Bundle savedInstanceState) {
                            super.onCreate(savedInstanceState);
                            setContentView(R.layout.activity_main);
                        }
                    }
                

                TextView tv = new TextView(this);
                LinearLayout.LayoutParams params = new LinearLayout.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.WRAP_CONTENT);
                tv.setLayoutParams(params);
                

                    public class MainActivity extends AppCompatActivity {
                        Context context;
                        @Override
                        protected void onCreate(Bundle savedInstanceState) {
                            super.onCreate(savedInstanceState);
                            context = this;
                            //create instance of linear layout
                            LinearLayout linearLayoutMain = new LinearLayout(context);
                            linearLayoutMain.setLayoutParams(new LinearLayout.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.MATCH_PARENT));
                            linearLayoutMain.setOrientation(LinearLayout.VERTICAL);
                            //add linearLayout as main container of activity
                            setContentView(linearLayoutMain);
                            //create textview
                            TextView textView = new TextView(context);
                            textView.setText("Hello World!");
                            textView.setLayoutParams(new LinearLayout.LayoutParams(ViewGroup.LayoutParams.WRAP_CONTENT, ViewGroup.LayoutParams.WRAP_CONTENT));
                            //set text view as child of linearlayout
                            linearLayoutMain.addView(textView);
                        }
                    }
                

                    <?xml version="1.0" encoding="utf-8"?>
                    <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
                            xmlns:app="http://schemas.android.com/apk/res-auto"
                            xmlns:tools="http://schemas.android.com/tools"
                            android:layout_width="match_parent"
                            android:layout_height="match_parent"
                            android:orientation="vertical"
                            tools:context=".MainActivity">
                        <TextView
                                android:id="@+id/text_view"
                                android:layout_width="wrap_content"
                                android:layout_height="wrap_content"
                                android:text="Hello World!" />
                    </LinearLayout>
                

                    public class MainActivity extends AppCompatActivity {
                        Context context;
                        @Override
                        protected void onCreate(Bundle savedInstanceState) {
                            super.onCreate(savedInstanceState);
                            context = this;
                            setContentView(R.layout.activity_main);
                            //access to textview
                            TextView textView = findViewById(R.id.text_view);
                            //change value of textview
                            textView.setText("New text to print");
                        }
                    }
                

                    <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
                            android:layout_width="match_parent"
                            android:layout_height="match_parent"
                            android:orientation="horizontal"
                            android:padding="5dp">
                        <TextView
                                android:layout_width="0dp"
                                android:layout_height="wrap_content"
                                android:layout_weight="10"
                                android:background="#f00"
                                android:gravity="center"
                                android:textSize="20dp"
                                android:textColor="#fff"
                                android:text="Left" />
                        <TextView
                                android:layout_width="0dp"
                                android:layout_height="wrap_content"
                                android:layout_weight="10"
                                android:background="#0f0"
                                android:gravity="center"
                                android:textSize="20dp"
                                android:textColor="#fff"
                                android:text="Right" />
                        <TextView
                                android:id="@+id/tv_view_number"
                                android:layout_width="0dp"
                                android:layout_height="wrap_content"
                                android:layout_weight="10"
                                android:background="#00f"
                                android:gravity="center"
                                android:textSize="20dp"
                                android:textColor="#fff"
                                android:text="No " />
                    </LinearLayout>
                

                    public class InflatorActivity extends AppCompatActivity {
                        Context context;
                        @Override
                        protected void onCreate(Bundle savedInstanceState) {
                            super.onCreate(savedInstanceState);
                            context = this;
                            LinearLayout llMain = new LinearLayout(context);
                            llMain.setOrientation(LinearLayout.VERTICAL);
                            setContentView(llMain);
                            for (int i = 0; i < 10; i++) {
                                //deserialization of view
                                LinearLayout linearLayoutSmallView = (LinearLayout) LayoutInflater.from(context).inflate(R.layout.small_view,null);
                                TextView textViewNumberView = linearLayoutSmallView.findViewById(R.id.tv_view_number);
                                textViewNumberView.setText("No : " + (i+1));
                                llMain.addView(linearLayoutSmallView);
                            }
                        }
                    }
                

                Intent intent = new Intent(ctx,ClassName.class);
                startActivity(intent);
            

                            Intent intent = new Intent(this, SecondeActivity.class);
                            intent.putExtra("name","user name");
                            intent.putExtra("id", "456-fesdf-464sdf");
                            intent.putExtra("year", 27);
                            startActivity(intent);
                        

                            Intent intent = getIntent();
                            String nameValue = intent.getStringExtra("name");
                            String idValue = intent.getStringExtra("id");
                            int yearValue =  intent.getIntExtra("year", -1);
                        

                ActivityResultLauncher<Intent> resultActivity = registerForActivityResult(
                        new ActivityResultContracts.StartActivityForResult(),
                        new ActivityResultCallback<ActivityResult>() {
                            @Override
                            public void onActivityResult(ActivityResult result) {
                                if (result.getResultCode() == RESULT_OK) {
                                    //do instruction when result
                                    Intent intent = result.getData();
                                    String dataString = intent.getStringExtra("dataKey");
                                }
                            }
                        }
                );
                Intent intent = new Intent(this, SecondeActivity.class);
                resultActivity.launch(intent);
            

                button.setOnClickListener(new View.OnClickListener() {
                    @Override
                    public void onClick(View v) {
                        Intent intent = new Intent();
                        intent.putExtra("dataKey","hello data"); //1
                        setResult(RESULT_OK, intent); //2
                        finish(); //3
                    }
                });
            

                    MyProject/
                        src/
                            MyActivity.java
                        res/
                            drawable/
                                graphic.png
                            layout/
                                main.xml
                                info.xml
                            mipmap/
                                icon.png
                            values/
                                strings.xml
                

                    public class R {
                        public static class layout{
                            public static final int activity_main = 0xabc123;
                            public static final int my_layout = 0xabc124;
                            public static final int other_layout = 0xabc125;
                        }
                        public static class drawable{
                            public static final int image1 = 0xbcd123;
                            public static final int image2 = 0xbcd124;
                            public static final int chat = 0xbcd125;
                        }
                        public static class string{
                            public static final int msg_welcom = 0xefa123;
                            public static final int app_name = 0xefa124;
                            public static final int msg_btn_send = 0xefa125;
                        }
                        public static class color{
                            public static final int color_texte = 0x456fa12;
                            public static final int color_btn = 0x456fa13;
                            public static final int color_border = 0x456fa14;
                            public static final int color_title = 0x456fa15;
                        }
                    }
                

                    Resources resources = context.getResources();
                    String stringRessource = resources.getString(R.string.key_ressource);
                    
                    //XXX resValue = resources.getXXX(id);
                

                    @[package:]type_ressource/nom_ressource
                

                    @+[package:]type/nom
                

                    <string name="dyn1">Hello %1$s, you have %2$d years</string>
                

                    Resources res = context.getResources();
                    String chaine = res.getString(R.string.dyn1, "durand", 32);
                

                    AssetManager assetManager = getAssets(); //into activity
                    AssetManager assetManager = context.getAssets(); // everywhere in application
                    try {
                        InputStream inputStream = assetManager.open("fileName");
                    } catch (IOException e) {
                        throw new RuntimeException(e);
                    }
                

                    InputStream inputStream = assetManager.open("fileName");
                    Drawable drawableImage = Drawable.createFromStream(inputStream, null);
                    Bitmap bitmapImage = BitmapFactory.decodeStream(inputStream);
                

                                <menu xmlns:android="http://schemas.android.com/apk/res/android"
                                    xmlns:app="http://schemas.android.com/apk/res-auto">
                                <item
                                        android:id="@+id/menu_play"
                                        android:icon="@android:drawable/ic_media_play"
                                        android:title="play"
                                        app:showAsAction="always" />
                                <item
                                        android:id="@+id/menu_stop"
                                        android:icon="@android:drawable/ic_media_stop"
                                        android:title="stop"
                                        app:showAsAction="always" />
                                <item
                                        android:id="@+id/menu_next"
                                        android:title="next"
                                        app:showAsAction="always" />
                                <item
                                        android:id="@+id/menu_pause"
                                        android:icon="@android:drawable/ic_media_pause"
                                        android:title="pause"
                                        app:showAsAction="ifRoom" />
                                <item
                                        android:id="@+id/menu_reset"
                                        android:title="reset"
                                        app:showAsAction="never" />
                            </menu>
                            

                @Override
                public boolean onCreateOptionsMenu(Menu menu) {
                    MenuInflater menuInflater = getMenuInflater();
                    menuInflater.inflate(R.menu.layout_menu, menu);
                    return true;
                }
            

                @Override
                public boolean onCreateOptionsMenu(Menu menu) {
                    int idItem = 1;        // exemple pour ajouter un item
                    int order = 1;
                    MenuItem menuItem = menu.add(0, idItem, order, "mon menu");
                    return true;
                }
            

                @Override
                public boolean onOptionsItemSelected(@NonNull MenuItem item) {
                    boolean retour = super.onOptionsItemSelected(item);
                    switch (item.getItemId()) {
                        case R.id.menu_play:
                            //action todo
                            retour = true;
                            break;
                        case R.id.menu_stop:
                            //action todo
                            retour = true;
                            break;
                        case R.id.menu_pause:
                            //action todo
                            retour = true;
                            break;
                        case R.id.menu_next:
                            //action todo
                            retour = true;
                            break;
                        case R.id.menu_reset:
                            //action todo
                            retour = true;
                            break;
                    }
                    return retour;
                }
            

                AlertDialog.Builder builder = new AlertDialog.Builder(context);
                builder.setTitle("my wonderful title");
                builder.setMessage("my beautiful Message to print ");
                AlertDialog dialog = builder.create();
                dialog.show();
                //or
                AlertDialog dialog = builder.show();
            

                AlertDialog.Builder builder = new AlertDialog.Builder(context);
                builder.setTitle("my wonderful title");
                builder.setMessage("my beautiful Message to print ");
                builder.setPositiveButton("Yes", new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialog, int which) {
                        //action if yes is select
                    }
                });
                builder.setNeutralButton("i don't know", new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialog, int which) {
                        //action if i don't know is select
                    }
                });
                builder.setPositiveButton("no", new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialog, int which) {
                        //action if no select
                    }
                });
                AlertDialog dialog = builder.show();
            

                String[] items = new String[]{"orange","blue","green"};
                AlertDialog.Builder builder = new AlertDialog.Builder(context);
                builder.setTitle("my wonderful title");
                builder.setItems(items, new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialog, int which) {
                        String value = items[which];//which = position of item select
                    }
                });
                AlertDialog dialog = builder.show();
            

                <string-array name="colors_list">
                    <item>orange</item>
                    <item>blue</item>
                    <item>green</item>
                </string-array>
            

                builder.setItems(R.array.colors_list, new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialog, int which) {
                        String[] items = getResources().getStringArray(R.array.colors_list); //pour récupérer les données depuis le répertoire Ressource
                        String value = items[which];//which = position of item select
                    }
                });
            

vue définie en xml

                <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
                        android:layout_width="match_parent"
                        android:layout_height="match_parent"
                        android:orientation="vertical">
                    <LinearLayout
                            android:layout_width="match_parent"
                            android:layout_height="wrap_content"
                            android:orientation="horizontal">
                        <TextView
                                android:layout_width="0px"
                                android:layout_height="wrap_content"
                                android:layout_weight="30"
                                android:text="login : " />
                        <EditText
                                android:id="@+id/ed_login_ad"
                                android:layout_width="0px"
                                android:layout_height="wrap_content"
                                android:layout_weight="70" />
                    </LinearLayout>
                    <LinearLayout
                            android:layout_width="match_parent"
                            android:layout_height="wrap_content"
                            android:orientation="horizontal">
                        <TextView
                                android:layout_width="0px"
                                android:layout_height="wrap_content"
                                android:layout_weight="30"
                                android:text="password : " />
                        <EditText
                                android:id="@+id/ed_password_ad"
                                android:layout_width="0px"
                                android:layout_height="wrap_content"
                                android:layout_weight="70" />
                    </LinearLayout>
                </LinearLayout>
            

code java pour un alert dialog avec une vue perso

                AlertDialog.Builder builder = new AlertDialog.Builder(context);
                builder.setTitle("my wonderful title");
                View view = LayoutInflater.from(context).inflate(R.layout.alert_dialog_layout,null);
                builder.setView(view);
                AlertDialog dialog = builder.show();
                

                EditText edLogin = view.findViewById(R.id.ed_login_ad);
            

                builder.setPositiveButton("Yes", new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialog, int which) {
                        AlertDialog alertDialog = (AlertDialog) dialog;
                        EditText edLogin = alertDialog.findViewById(R.id.ed_login_ad);
                    }
                });
            

                    view.setOnClickListener(new View.OnClickListener() {
                        @Override
                        public void onClick(View v) {
                            //action to do
                            v.setBackgroundColor(Color.GREEN);
                        }
                    });
                

                    view.setOnLongClickListener(new View.OnLongClickListener() {
                        @Override
                        public boolean onLongClick(View v) {
                            return true;
                        }
                    });
                

                    view.setOnFocusChangeListener(new View.OnFocusChangeListener() {
                        @Override
                        public void onFocusChange(View v, boolean hasFocus) {
                            if(hasFocus){
                                v.setBackgroundColor(Color.GREEN);
                            }else{
                                v.setBackgroundColor(Color.BLUE);
                            }
                        }
                    });
                

                    editText.addTextChangedListener(new TextWatcher() {
                        @Override
                        public void beforeTextChanged(CharSequence s, int start, int count, int after) {
                        }
                        @Override
                        public void onTextChanged(CharSequence s, int start, int before, int count) {
                        }
                        @Override
                        public void afterTextChanged(Editable s) {
                        }
                    });
                

                    radioButton.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {
                        @Override
                        public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
                        }
                    });
                

                    public class MainActivity extends AppCompactActivity {
                    ...
                    // exemple pour une activité, mais même approche pour une sous classe de View
                    @Override
                    public boolean onTouchEvent(MotionEvent event){
                    
                        int action = MotionEventCompat.getActionMasked(event);
                    
                        switch(action) {
                            case (MotionEvent.ACTION_DOWN) :
                                Log.d(DEBUG_TAG,"Action was DOWN");
                                return true;
                            case (MotionEvent.ACTION_MOVE) :
                                Log.d(DEBUG_TAG,"Action was MOVE");
                                return true;
                            case (MotionEvent.ACTION_UP) :
                                Log.d(DEBUG_TAG,"Action was UP");
                                return true;
                            case (MotionEvent.ACTION_OUTSIDE) :
                                Log.d(DEBUG_TAG,"Movement occurred outside bounds " +
                                        "of current screen element");
                                return true;
                            default :
                                return super.onTouchEvent(event);
                        }
                    }
                    
                    //exemple sur une sous-classe de View
                    View myView = findViewById(R.id.my_view);
                    myView.setOnTouchListener(new OnTouchListener() {
                        public boolean onTouch(View v, MotionEvent event) {
                            //action to do
                            return true;
                        }
                    });
                    
                

                    @Override
                    public boolean onTouchEvent(MotionEvent event) {
                        float xPosition = 0;
                        float yPosition = 0;
                        if(event.getActionMasked() == MotionEvent.ACTION_DOWN){
                            xPosition = event.getX();
                            yPosition = event.getY();
                        }
                        if(event.getActionMasked() == MotionEvent.ACTION_MOVE){
                            xPosition = event.getX();
                            yPosition = event.getY();
                        }
                        return super.onTouchEvent(event);
                    }
                

                    @Override
                    public boolean onTouchEvent(MotionEvent event) {
                        // get pointer index from the event object
                        int pointerIndex = event.getActionIndex();
                        // get pointer ID from pointerIndex
                        int pointerId = event.getPointerId(pointerIndex);
                        // get action
                        int maskedAction = event.getActionMasked();
                        switch (maskedAction) {
                            case MotionEvent.ACTION_DOWN:
                                Log.d(TAG, "index down: " + pointerId);
                                break;
                            case MotionEvent.ACTION_POINTER_DOWN: {
                                Log.d(TAG, "index down: " + pointerId);
                                break;
                            }
                            case MotionEvent.ACTION_MOVE: { // a pointer was moved
                                Log.d(TAG, "index move: " + pointerId);
                                break;
                            }
                            case MotionEvent.ACTION_UP:
                                Log.d(TAG, "index up: " + pointerId);
                
                                break;
                            case MotionEvent.ACTION_POINTER_UP:
                                Log.d(TAG, "index up: " + pointerId);
                                break;
                        }
                
                        return true;
                    }
                

                            public class EventActivity extends AppCompatActivity implements GestureDetector.OnGestureListener {
                                Context context;
                                @Override
                                protected void onCreate(Bundle savedInstanceState) {
                                    super.onCreate(savedInstanceState);
                                    context = this;
                                    setContentView(R.layout.activity_event);
                                }
                                @Override
                                public boolean onDown(MotionEvent e) {
                                    return false;
                                }
                                @Override
                                public void onShowPress(MotionEvent e) {
                                }
                                @Override
                                public boolean onSingleTapUp(MotionEvent e) {
                                    return false;
                                }
                                @Override
                                public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY) {
                                    return false;
                                }
                                @Override
                                public void onLongPress(MotionEvent e) {
                                }
                                @Override
                                public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY) {
                                    return false;
                                }
                            }
                        

                    public class EventActivity extends AppCompatActivity implements GestureDetector.OnGestureListener {
                        private String TAG = "debug-app";
                        GestureDetector gestureDetector;
                        Context context;
                        @Override
                        protected void onCreate(Bundle savedInstanceState) {
                            super.onCreate(savedInstanceState);
                            context = this;
                            setContentView(R.layout.activity_event);
                            gestureDetector = new GestureDetector(this,this);
                        }
                        @Override
                        public boolean onDown(MotionEvent e) {
                            return false;
                        }
                        @Override
                        public void onShowPress(MotionEvent e) {
                        }
                        @Override
                        public boolean onSingleTapUp(MotionEvent e) {
                            return false;
                        }
                        @Override
                        public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY) {
                            return false;
                        }
                        @Override
                        public void onLongPress(MotionEvent e) {
                        }
                        @Override
                        public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY) {
                            return false;
                        }
                    }
                

                    public class EventActivity extends AppCompatActivity implements GestureDetector.OnGestureListener {
                        private String TAG = "debug-app";
                        GestureDetector gestureDetector;
                        Context context;
                        @Override
                        protected void onCreate(Bundle savedInstanceState) {
                            super.onCreate(savedInstanceState);
                            context = this;
                            setContentView(R.layout.activity_event);
                            gestureDetector = new GestureDetector(this,this);
                        }
                        @Override
                        public boolean onTouchEvent(MotionEvent event) {
                            gestureDetector.onTouchEvent(event);
                            return true;
                        }
                        @Override
                        public boolean onDown(MotionEvent e) {
                            return false;
                        }
                        @Override
                        public void onShowPress(MotionEvent e) {
                        }
                        @Override
                        public boolean onSingleTapUp(MotionEvent e) {
                            return false;
                        }
                        @Override
                        public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY) {
                            return false;
                        }
                        @Override
                        public void onLongPress(MotionEvent e) {
                        }
                        @Override
                        public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY) {
                            return false;
                        }
                    }
                

                //si pas besoin de catégoriser les informations
                SharedPreferences sharedPreferences = PreferenceManager.getDefaultSharedPreferences(this);
                //si besoin de catégoriser
                SharedPreferences sharedPreferencesUser = context.getSharedPreferences("user", Context.MODE_PRIVATE);
            

                SharedPreferences sharedPreferences = PreferenceManager.getDefaultSharedPreferences(this);
                String guid = sharedPreferences.getString("id",null);
                int age = sharedPreferences.getInt("age",-1);
            

                SharedPreferences sharedPreferences = PreferenceManager.getDefaultSharedPreferences(this);
                SharedPreferences.Editor editor = sharedPreferences.edit();
                editor.putString("userName", "John Doe");
                editor.putFloat("xPosition", 42.56f);
                editor.putFloat("yPosition", 1056.89f);
                editor.apply();
            

                SharedPreferences sharedPreferences = PreferenceManager.getDefaultSharedPreferences(this);
                SharedPreferences.Editor editor = sharedPreferences.edit();
               
                //suppression par clef
                editor.remove("userName");
                editor.remove("id");
                editor.apply();
               
                //suppression total
                editor.clear();
                editor.apply();
            

            File file = new File(context.getFilesDir(), filename);
            

                String filename = "myFile.txt";
                String fileContents = "Hello world!";
                try (FileOutputStream fos = context.openFileOutput(filename, Context.MODE_PRIVATE)) {
                    fos.write(fileContents.toByteArray());
                }
            

                FileInputStream fileInputStream = context.openFileInput(fileName);
                InputStreamReader inputStreamReader =
                        new InputStreamReader(fileInputStream, StandardCharsets.UTF_8);
                StringBuilder stringBuilder = new StringBuilder();
                try (BufferedReader reader = new BufferedReader(inputStreamReader)) {
                    String line = reader.readLine();
                    while (line != null) {
                        stringBuilder.append(line).append('\n');
                        line = reader.readLine();
                    }
                } catch (IOException e) {
                    // Error occurred when opening raw file for reading.
                } finally {
                    String contents = stringBuilder.toString();
                }
            

                <uses-permission android:name="android.permission.MANAGE_EXTERNAL_STORAGE" />
            

                    File file = new File(Environment.getExternalStorageDirectory().getPath()+ File.separator+ "Android/data"+File.separator + getPackageName() + "/files/"+"myFile.txt" );
                

                CREATE TABLE etudiant (
                    id INTEGER PRIMARY KEY AUTOINCREMENT,
                    first_name TEXT,
                    last_name TEXT,
                    age
                );
            

                public class DataBaseHelper extends SQLiteOpenHelper {
                    public DataBaseHelper(@Nullable Context context, @Nullable String name, @Nullable SQLiteDatabase.CursorFactory factory, int version) {
                        super(context, name, factory, version);
                    }
                    @Override
                    public void onCreate(SQLiteDatabase db) {
                    }
                    @Override
                    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
                    }
                }
            

                @Override
                public void onCreate(SQLiteDatabase db) {
                    db.execSQL("CREATE TABLE etudiant (\n" +
                            "id INTEGER PRIMARY KEY AUTOINCREMENT," +
                            "first_name TEXT," +
                            "last_name TEXT," +
                            "age" +
                            ");");
                    db.execSQL("INSERT INTO etudiant ('first_name','last_name','age') values ('john','doe', 27), ('foo','bar',99);");
                }
                @Override
                public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
                    db.execSQL("DROP TABLE IF EXISTS etudiant");
                    onCreate(db);
                }
            

                public class ConnectionDB {
                    private static int version = 1;
                    private static String bnName = "myBd.db";
                    private static SQLiteDatabase bd = null;
                    private static DataBaseHelper helper;
                    
                    public static SQLiteDatabase getBd(Context context){
                        if(helper == null){
                            helper = new DataBaseHelper(context, bnName, null, version);
                        }
                        bd = helper.getWritableDatabase();
                        return bd;
                    }
                    public static void close(){
                        if(bd!= null &&  !bd.isOpen()){
                            bd.close();
                        }
                    }
                }
            

                    public class EtudiantManager {
                    
                        public static long add(Context context, Etudiant etudiantToAdd){
                            ContentValues contentValues = new ContentValues();
                            contentValues.put("first_name", etudiantToAdd.getFirstName());
                            contentValues.put("last_name", etudiantToAdd.getLastName());
                            contentValues.put("age", etudiantToAdd.getAge());
                            SQLiteDatabase bd = ConnectionDB.getBd(context); //on réutilise ConnctionDB ici
                            return bd.insert("etudiant", null, contentValues);
                        }
                    }
                

                public static void delete(Context context, int idEtudiant){
                    SQLiteDatabase bd = ConnectionDB.getBd(context);
                    bd.delete("etudiant","id = ?" , new String[]{String.valueOf(idEtudiant)});
                }
            

                public int delete (String table,
                                    String whereClause,
                                    String[] whereArgs)
            

                DELETE FROM etudiant WHERE id = ?
            

                DELETE FROM etudiant WHERE id = 7
            

                    DELETE FROM etudiant WHERE id = ? AND name LIKE ?
                

                    public static void update(Context context, Etudiant etudiantToUpdate) {
                        ContentValues contentValues = new ContentValues();
                        contentValues.put("first_name", etudiantToUpdate.getFirstName());
                        contentValues.put("age", etudiantToUpdate.getAge());
                        SQLiteDatabase bd = ConnectionDB.getBd(context);
                        long nbRowChange = bd.update("etudiant", contentValues, "id = ?", new String[]{String.valueOf(etudiantToUpdate.getId())});
                    }
                

                    public static ArrayList<Etudiant> getAll(Context context) {
                        SQLiteDatabase bd = ConnectionDB.getBd(context);
                        String query = "SELECT * FROM etudiant";
                        ArrayList<Etudiant> etudiants = null;
                        Cursor cursor = bd.rawQuery(query, null);
                        if (cursor.isBeforeFirst()) {
                            etudiants = new ArrayList<>();
                            while (cursor.moveToNext()) {
                                Etudiant etudiant = new Etudiant();
                                etudiant.setId(cursor.getInt(cursor.getColumnIndexOrThrow("id")));
                                etudiant.setFirstName(cursor.getString(cursor.getColumnIndexOrThrow("first_name")));
                                etudiant.setLastName(cursor.getString(cursor.getColumnIndexOrThrow("last_name")));
                                etudiant.setAge(cursor.getInt(cursor.getColumnIndexOrThrow("age")));
                                etudiants.add(etudiant);
                            }
                        }
                        return etudiants;
                    }
                

                public static ArrayList<Etudiant> getByAgeLimite(Context context, int ageLimite) {
                    SQLiteDatabase bd = ConnectionDB.getBd(context);
                    String query = "SELECT * FROM etudiant where age > ?";
                    ArrayList<Etudiant> etudiants = null;
                    Cursor cursor = bd.rawQuery(query, new String[]{String.valueOf(ageLimite)});
                    if (cursor.isBeforeFirst()) {
                        etudiants = new ArrayList<>();
                        while (cursor.moveToNext()) {
                            Etudiant etudiant = new Etudiant();
                            etudiant.setId(cursor.getInt(cursor.getColumnIndexOrThrow("id")));
                            etudiant.setFirstName(cursor.getString(cursor.getColumnIndexOrThrow("first_name")));
                            etudiant.setLastName(cursor.getString(cursor.getColumnIndexOrThrow("last_name")));
                            etudiant.setAge(cursor.getInt(cursor.getColumnIndexOrThrow("age")));
                            etudiants.add(etudiant);
                        }
                    }
                    return etudiants;
                }
                

                    SensorManager sensorManager = (SensorManager) getSystemService(Context.SENSOR_SERVICE);
                

                    List<Sensor> sensors = sensorManager.getSensorList(Sensor.TYPE_ALL);
                    for (Sensor sensor : sensors) {
                        Log.d("debug_app", "sensor: " + sensor.getName());
                        Log.d("debug_app", "sensor: " + sensor.getMinDelay());
                        Log.d("debug_app", "sensor: " + sensor.getVersion());
                        Log.d("debug_app", "sensor: " + sensor.getMaximumRange());
                    }
                

                    Sensor sensorLight = sensorManager.getDefaultSensor(Sensor.TYPE_LIGHT);
                    if(sensorLight != null){
                        // sensor existe
                    } else {
                        // prévenir l'utilisateur qu'on ne peut pas continuer
                    }
                

                SensorEventListener sensorEventListener = new SensorEventListener() {
                    @Override
                    public void onSensorChanged(SensorEvent event) {
                    }
                    @Override
                    public void onAccuracyChanged(Sensor sensor, int accuracy) {
                    }
                };
                

                    @Override
                    protected void onResume() {
                        super.onResume();
                        sensorManager.registerListener(sensorEventListener, sensorLight, SensorManager.SENSOR_DELAY_FASTEST);
                    }
                

                    @Override
                    protected void onPause() {
                        super.onPause();
                        sensorManager.unregisterListener(sensorEventListener,sensorLight);
                    }
                

                    public class SensorActivity extends AppCompatActivity {
                        TextView textView;
                        SensorManager sensorManager;
                        SensorEventListener sensorEventListener;
                        Sensor sensorLight;
                        @Override
                        protected void onCreate(Bundle savedInstanceState) {
                            super.onCreate(savedInstanceState);
                            setContentView(R.layout.activity_sensor);
                            textView = findViewById(R.id.text);
                            sensorManager = (SensorManager) getSystemService(Context.SENSOR_SERVICE);
                            sensorLight = sensorManager.getDefaultSensor(Sensor.TYPE_LIGHT);
                            sensorEventListener = new SensorEventListener() {
                                @Override
                                public void onSensorChanged(SensorEvent event) {
                                    float luxValue = event.values[0];
                                    textView.setText(String.valueOf(luxValue) + " lux");
                                }
                                @Override
                                public void onAccuracyChanged(Sensor sensor, int accuracy) {
                                }
                            };
                        }
                        @Override
                        protected void onResume() {
                            super.onResume();
                            sensorManager.registerListener(sensorEventListener, sensorLight, SensorManager.SENSOR_DELAY_FASTEST);
                        }
                        @Override
                        protected void onPause() {
                            super.onPause();
                            sensorManager.unregisterListener(sensorEventListener,sensorLight);
                        }
                    }
                

                    <uses-feature android:name="android.hardware.sensor.accelerometer"
                                  android:required="true" />
                

                    <?xml version="1.0" encoding="utf-8"?>
                    <manifest
                        xmlns:android="http://schemas.android.com/apk/res/android"
                        android:versionCode="1"
                        android:versionName="1.0">
                    
                        <uses-feature android:name="android.hardware.sensor.compass"
                            android:required="true" />
                    
                        <application
                            android:allowBackup="true"
                            android:icon="@mipmap/ic_launcher"
                            android:roundIcon="@mipmap/ic_launcher_round"
                            android:label="@string/app_name"
                            android:supportsRtl="true"
                            android:theme="@style/AppTheme">
                    
                            <activity android:name=".MainActivity">
                                <intent-filter>
                                    <action android:name="android.intent.action.MAIN" />
                                    <category android:name="android.intent.category.LAUNCHER" />
                                </intent-filter>
                            </activity>
                            <activity
                                android:name=".DisplayMessageActivity"
                                android:parentActivityName=".MainActivity" />
                        </application>
                    </manifest>
            

                plugins {
                    id 'com.android.application'
                }
                android {
                    namespace 'com.example.appname'
                    compileSdk 32
                    defaultConfig {
                        applicationId "com.example.appname"
                        minSdk 25
                        targetSdk 32
                        versionCode 1
                        versionName "1.0"
                        testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
                    }
                    buildTypes {
                        release {
                            minifyEnabled false
                            proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
                        }
                    }
                    compileOptions {
                        sourceCompatibility JavaVersion.VERSION_1_8
                        targetCompatibility JavaVersion.VERSION_1_8
                    }
                }
                dependencies {
                    implementation 'androidx.appcompat:appcompat:1.5.1'
                    implementation 'com.google.android.material:material:1.7.0'
                    implementation 'androidx.constraintlayout:constraintlayout:2.1.4'
                    testImplementation 'junit:junit:4.13.2'
                    androidTestImplementation 'androidx.test.ext:junit:1.1.3'
                    androidTestImplementation 'androidx.test.espresso:espresso-core:3.4.0'
                }
            

                    public class MainActivity extends AppCompatActivity {
                        @Override
                        protected void onCreate(Bundle savedInstanceState) {
                            super.onCreate(savedInstanceState);
                            setContentView(R.layout.activity_main);
                        }
                    }
                

                public class MainActivity extends AppCompatActivity {
                    private static final String TAG = "debug_app";
                    @Override
                    protected void onCreate(Bundle savedInstanceState) {
                        super.onCreate(savedInstanceState);
                        setContentView(R.layout.activity_main);
                        Log.d(TAG, "onCreate:");
                    }
                    @Override
                    protected void onStart() {
                        super.onStart();
                        Log.d(TAG, "onStart: ");
                    }
                    @Override
                    protected void onResume() {
                        super.onResume();
                        Log.d(TAG, "onResume: ");
                    }
                    @Override
                    protected void onPause() {
                        super.onPause();
                        Log.d(TAG, "onPause: ");
                    }
                    @Override
                    protected void onStop() {
                        super.onStop();
                        Log.d(TAG, "onStop: ");
                    }
                    @Override
                    protected void onDestroy() {
                        super.onDestroy();
                        Log.d(TAG, "onDestroy: ");
                    }
                }
            

                public class FirstActivity extends Activity {
                }
            

                public class FirstActivity extends AppCompatActivity {
                    @Override
                    protected void onCreate(@Nullable Bundle savedInstanceState) {
                        super.onCreate(savedInstanceState);
                        setContentView(R.layout.activity_first);
                    }
                }
            

                <application
                       ... >
                    <activity android:name=".FirstActivity"
                        android:exported="true">
                        <intent-filter>
                            <action android:name="android.intent.action.MAIN" />
                            <category android:name="android.intent.category.LAUNCHER" />
                        </intent-filter>
                    </activity>
                </application>
            

                <application
                       ... >
                    <activity android:name=".FirstActivity"
                        android:exported="true">
                        <intent-filter>
                            <action android:name="android.intent.action.MAIN" />
                            <category android:name="android.intent.category.LAUNCHER" />
                        </intent-filter>
                    </activity>
                    <activity android:name=".SecondActivité"
                        android:exported="false"/>
                </application>
            

                public class MainActivity extends AppCompatActivity {
                    Context context;
                    @Override
                    protected void onCreate(Bundle savedInstanceState) {
                        super.onCreate(savedInstanceState);
                        context = this; //don t forget this line, else you will have NullPointer
                        setContentView(R.layout.activity_main);
                    }
                }
            

                    android:id="@+id/my_id"
                

                    <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
                            xmlns:app="http://schemas.android.com/apk/res-auto"
                            xmlns:tools="http://schemas.android.com/tools"
                            android:layout_width="match_parent"
                            android:layout_height="match_parent"
                            android:orientation="vertical"
                            tools:context=".MainActivity">
                        <TextView
                                android:layout_width="match_parent"
                                android:layout_height="wrap_content"
                                android:text="Hello World!" />
                        <TextView
                                android:layout_width="wrap_content"
                                android:layout_height="wrap_content"
                                android:layout_gravity="right"
                                android:text="Hello World!" />
                        <TextView
                                android:layout_width="match_parent"
                                android:gravity="right"
                                android:layout_height="wrap_content"
                                android:text="Hello World!" />
                        <TextView
                                android:layout_width="wrap_content"
                                android:layout_height="wrap_content"
                                android:layout_gravity="center"
                                android:text="Hello World!" />
                    </LinearLayout>
                

                    <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
                            xmlns:app="http://schemas.android.com/apk/res-auto"
                            xmlns:tools="http://schemas.android.com/tools"
                            android:layout_width="match_parent"
                            android:layout_height="match_parent"
                            android:orientation="vertical"
                            tools:context=".MainActivity">
                        <Button
                                android:layout_width="match_parent"
                                android:layout_height="0dp"
                                android:layout_weight="40"
                                android:text="btn 1" />
                        <Button
                                android:layout_width="match_parent"
                                android:layout_height="0dp"
                                android:layout_weight="60"
                                android:text="btn 2" />
                    </LinearLayout>
                

                    <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
                            xmlns:app="http://schemas.android.com/apk/res-auto"
                            xmlns:tools="http://schemas.android.com/tools"
                            android:layout_width="match_parent"
                            android:layout_height="match_parent"
                            android:orientation="horizontal"
                            tools:context=".MainActivity">
                        <Button
                                android:layout_width="0dp"
                                android:layout_height="match_parent"
                                android:layout_weight="2"
                                android:text="btn 1" />
                        <Button
                                android:layout_width="0dp"
                                android:layout_height="match_parent"
                                android:layout_weight="5"
                                android:text="btn 2" />
                    </LinearLayout>
                

                    public class MainActivity extends AppCompatActivity {
                        Context context;
                        @Override
                        protected void onCreate(Bundle savedInstanceState) {
                            super.onCreate(savedInstanceState);
                            context = this;
                            //set UI width XML File
                            setContentView(R.layout.activity_main); //we give here reference of XML file
                            
                            //set view width Java File
                            LinearLayout container = new LinearLayout(context);
                            setContentView(container);
                        }
                    }
                

                        <?xml version="1.0" encoding="utf-8"?>
                        <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
                                xmlns:app="http://schemas.android.com/apk/res-auto"
                                xmlns:tools="http://schemas.android.com/tools"
                                android:layout_width="match_parent"
                                android:layout_height="match_parent"
                                android:orientation="vertical"
                                tools:context=".MainActivity">
                            <TextView
                                    android:layout_width="wrap_content"
                                    android:layout_height="wrap_content"
                                    android:text="Hello World!" />
                        </LinearLayout>
                

                    public class MainActivity extends AppCompatActivity {
                        @Override
                        protected void onCreate(Bundle savedInstanceState) {
                            super.onCreate(savedInstanceState);
                            setContentView(R.layout.activity_main);
                        }
                    }
                

                TextView tv = new TextView(this);
                LinearLayout.LayoutParams params = new LinearLayout.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.WRAP_CONTENT);
                tv.setLayoutParams(params);
                

                    public class MainActivity extends AppCompatActivity {
                        Context context;
                        @Override
                        protected void onCreate(Bundle savedInstanceState) {
                            super.onCreate(savedInstanceState);
                            context = this;
                            //create instance of linear layout
                            LinearLayout linearLayoutMain = new LinearLayout(context);
                            linearLayoutMain.setLayoutParams(new LinearLayout.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.MATCH_PARENT));
                            linearLayoutMain.setOrientation(LinearLayout.VERTICAL);
                            //add linearLayout as main container of activity
                            setContentView(linearLayoutMain);
                            //create textview
                            TextView textView = new TextView(context);
                            textView.setText("Hello World!");
                            textView.setLayoutParams(new LinearLayout.LayoutParams(ViewGroup.LayoutParams.WRAP_CONTENT, ViewGroup.LayoutParams.WRAP_CONTENT));
                            //set text view as child of linearlayout
                            linearLayoutMain.addView(textView);
                        }
                    }
                

                    <?xml version="1.0" encoding="utf-8"?>
                    <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
                            xmlns:app="http://schemas.android.com/apk/res-auto"
                            xmlns:tools="http://schemas.android.com/tools"
                            android:layout_width="match_parent"
                            android:layout_height="match_parent"
                            android:orientation="vertical"
                            tools:context=".MainActivity">
                        <TextView
                                android:id="@+id/text_view"
                                android:layout_width="wrap_content"
                                android:layout_height="wrap_content"
                                android:text="Hello World!" />
                    </LinearLayout>
                

                    public class MainActivity extends AppCompatActivity {
                        Context context;
                        @Override
                        protected void onCreate(Bundle savedInstanceState) {
                            super.onCreate(savedInstanceState);
                            context = this;
                            setContentView(R.layout.activity_main);
                            //access to textview
                            TextView textView = findViewById(R.id.text_view);
                            //change value of textview
                            textView.setText("New text to print");
                        }
                    }
                

                    <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
                            android:layout_width="match_parent"
                            android:layout_height="match_parent"
                            android:orientation="horizontal"
                            android:padding="5dp">
                        <TextView
                                android:layout_width="0dp"
                                android:layout_height="wrap_content"
                                android:layout_weight="10"
                                android:background="#f00"
                                android:gravity="center"
                                android:textSize="20dp"
                                android:textColor="#fff"
                                android:text="Left" />
                        <TextView
                                android:layout_width="0dp"
                                android:layout_height="wrap_content"
                                android:layout_weight="10"
                                android:background="#0f0"
                                android:gravity="center"
                                android:textSize="20dp"
                                android:textColor="#fff"
                                android:text="Right" />
                        <TextView
                                android:id="@+id/tv_view_number"
                                android:layout_width="0dp"
                                android:layout_height="wrap_content"
                                android:layout_weight="10"
                                android:background="#00f"
                                android:gravity="center"
                                android:textSize="20dp"
                                android:textColor="#fff"
                                android:text="No " />
                    </LinearLayout>
                

                    public class InflatorActivity extends AppCompatActivity {
                        Context context;
                        @Override
                        protected void onCreate(Bundle savedInstanceState) {
                            super.onCreate(savedInstanceState);
                            context = this;
                            LinearLayout llMain = new LinearLayout(context);
                            llMain.setOrientation(LinearLayout.VERTICAL);
                            setContentView(llMain);
                            for (int i = 0; i < 10; i++) {
                                //deserialization of view
                                LinearLayout linearLayoutSmallView = (LinearLayout) LayoutInflater.from(context).inflate(R.layout.small_view,null);
                                TextView textViewNumberView = linearLayoutSmallView.findViewById(R.id.tv_view_number);
                                textViewNumberView.setText("No : " + (i+1));
                                llMain.addView(linearLayoutSmallView);
                            }
                        }
                    }
                

                Intent intent = new Intent(ctx,ClassName.class);
                startActivity(intent);
            

                            Intent intent = new Intent(this, SecondeActivity.class);
                            intent.putExtra("name","user name");
                            intent.putExtra("id", "456-fesdf-464sdf");
                            intent.putExtra("year", 27);
                            startActivity(intent);
                        

                            Intent intent = getIntent();
                            String nameValue = intent.getStringExtra("name");
                            String idValue = intent.getStringExtra("id");
                            int yearValue =  intent.getIntExtra("year", -1);
                        

                ActivityResultLauncher<Intent> resultActivity = registerForActivityResult(
                        new ActivityResultContracts.StartActivityForResult(),
                        new ActivityResultCallback<ActivityResult>() {
                            @Override
                            public void onActivityResult(ActivityResult result) {
                                if (result.getResultCode() == RESULT_OK) {
                                    //do instruction when result
                                    Intent intent = result.getData();
                                    String dataString = intent.getStringExtra("dataKey");
                                }
                            }
                        }
                );
                Intent intent = new Intent(this, SecondeActivity.class);
                resultActivity.launch(intent);
            

                button.setOnClickListener(new View.OnClickListener() {
                    @Override
                    public void onClick(View v) {
                        Intent intent = new Intent();
                        intent.putExtra("dataKey","hello data"); //1
                        setResult(RESULT_OK, intent); //2
                        finish(); //3
                    }
                });
            

                    MyProject/
                        src/
                            MyActivity.java
                        res/
                            drawable/
                                graphic.png
                            layout/
                                main.xml
                                info.xml
                            mipmap/
                                icon.png
                            values/
                                strings.xml
                

                    public class R {
                        public static class layout{
                            public static final int activity_main = 0xabc123;
                            public static final int my_layout = 0xabc124;
                            public static final int other_layout = 0xabc125;
                        }
                        public static class drawable{
                            public static final int image1 = 0xbcd123;
                            public static final int image2 = 0xbcd124;
                            public static final int chat = 0xbcd125;
                        }
                        public static class string{
                            public static final int msg_welcom = 0xefa123;
                            public static final int app_name = 0xefa124;
                            public static final int msg_btn_send = 0xefa125;
                        }
                        public static class color{
                            public static final int color_texte = 0x456fa12;
                            public static final int color_btn = 0x456fa13;
                            public static final int color_border = 0x456fa14;
                            public static final int color_title = 0x456fa15;
                        }
                    }
                

                    Resources resources = context.getResources();
                    String stringRessource = resources.getString(R.string.key_ressource);
                    
                    //XXX resValue = resources.getXXX(id);
                

                    @[package:]type_ressource/nom_ressource
                

                    @+[package:]type/nom
                

                    <string name="dyn1">Hello %1$s, you have %2$d years</string>
                

                    Resources res = context.getResources();
                    String chaine = res.getString(R.string.dyn1, "durand", 32);
                

                    AssetManager assetManager = getAssets(); //into activity
                    AssetManager assetManager = context.getAssets(); // everywhere in application
                    try {
                        InputStream inputStream = assetManager.open("fileName");
                    } catch (IOException e) {
                        throw new RuntimeException(e);
                    }
                

                    InputStream inputStream = assetManager.open("fileName");
                    Drawable drawableImage = Drawable.createFromStream(inputStream, null);
                    Bitmap bitmapImage = BitmapFactory.decodeStream(inputStream);
                

                                <menu xmlns:android="http://schemas.android.com/apk/res/android"
                                    xmlns:app="http://schemas.android.com/apk/res-auto">
                                <item
                                        android:id="@+id/menu_play"
                                        android:icon="@android:drawable/ic_media_play"
                                        android:title="play"
                                        app:showAsAction="always" />
                                <item
                                        android:id="@+id/menu_stop"
                                        android:icon="@android:drawable/ic_media_stop"
                                        android:title="stop"
                                        app:showAsAction="always" />
                                <item
                                        android:id="@+id/menu_next"
                                        android:title="next"
                                        app:showAsAction="always" />
                                <item
                                        android:id="@+id/menu_pause"
                                        android:icon="@android:drawable/ic_media_pause"
                                        android:title="pause"
                                        app:showAsAction="ifRoom" />
                                <item
                                        android:id="@+id/menu_reset"
                                        android:title="reset"
                                        app:showAsAction="never" />
                            </menu>
                            

                @Override
                public boolean onCreateOptionsMenu(Menu menu) {
                    MenuInflater menuInflater = getMenuInflater();
                    menuInflater.inflate(R.menu.layout_menu, menu);
                    return true;
                }
            

                @Override
                public boolean onCreateOptionsMenu(Menu menu) {
                    int idItem = 1;        // exemple pour ajouter un item
                    int order = 1;
                    MenuItem menuItem = menu.add(0, idItem, order, "mon menu");
                    return true;
                }
            

                @Override
                public boolean onOptionsItemSelected(@NonNull MenuItem item) {
                    boolean retour = super.onOptionsItemSelected(item);
                    switch (item.getItemId()) {
                        case R.id.menu_play:
                            //action todo
                            retour = true;
                            break;
                        case R.id.menu_stop:
                            //action todo
                            retour = true;
                            break;
                        case R.id.menu_pause:
                            //action todo
                            retour = true;
                            break;
                        case R.id.menu_next:
                            //action todo
                            retour = true;
                            break;
                        case R.id.menu_reset:
                            //action todo
                            retour = true;
                            break;
                    }
                    return retour;
                }
            

                AlertDialog.Builder builder = new AlertDialog.Builder(context);
                builder.setTitle("my wonderful title");
                builder.setMessage("my beautiful Message to print ");
                AlertDialog dialog = builder.create();
                dialog.show();
                //or
                AlertDialog dialog = builder.show();
            

                AlertDialog.Builder builder = new AlertDialog.Builder(context);
                builder.setTitle("my wonderful title");
                builder.setMessage("my beautiful Message to print ");
                builder.setPositiveButton("Yes", new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialog, int which) {
                        //action if yes is select
                    }
                });
                builder.setNeutralButton("i don't know", new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialog, int which) {
                        //action if i don't know is select
                    }
                });
                builder.setPositiveButton("no", new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialog, int which) {
                        //action if no select
                    }
                });
                AlertDialog dialog = builder.show();
            

                String[] items = new String[]{"orange","blue","green"};
                AlertDialog.Builder builder = new AlertDialog.Builder(context);
                builder.setTitle("my wonderful title");
                builder.setItems(items, new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialog, int which) {
                        String value = items[which];//which = position of item select
                    }
                });
                AlertDialog dialog = builder.show();
            

                <string-array name="colors_list">
                    <item>orange</item>
                    <item>blue</item>
                    <item>green</item>
                </string-array>
            

                builder.setItems(R.array.colors_list, new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialog, int which) {
                        String[] items = getResources().getStringArray(R.array.colors_list); //pour récupérer les données depuis le répertoire Ressource
                        String value = items[which];//which = position of item select
                    }
                });
            

vue définie en xml

                <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
                        android:layout_width="match_parent"
                        android:layout_height="match_parent"
                        android:orientation="vertical">
                    <LinearLayout
                            android:layout_width="match_parent"
                            android:layout_height="wrap_content"
                            android:orientation="horizontal">
                        <TextView
                                android:layout_width="0px"
                                android:layout_height="wrap_content"
                                android:layout_weight="30"
                                android:text="login : " />
                        <EditText
                                android:id="@+id/ed_login_ad"
                                android:layout_width="0px"
                                android:layout_height="wrap_content"
                                android:layout_weight="70" />
                    </LinearLayout>
                    <LinearLayout
                            android:layout_width="match_parent"
                            android:layout_height="wrap_content"
                            android:orientation="horizontal">
                        <TextView
                                android:layout_width="0px"
                                android:layout_height="wrap_content"
                                android:layout_weight="30"
                                android:text="password : " />
                        <EditText
                                android:id="@+id/ed_password_ad"
                                android:layout_width="0px"
                                android:layout_height="wrap_content"
                                android:layout_weight="70" />
                    </LinearLayout>
                </LinearLayout>
            

code java pour un alert dialog avec une vue perso

                AlertDialog.Builder builder = new AlertDialog.Builder(context);
                builder.setTitle("my wonderful title");
                View view = LayoutInflater.from(context).inflate(R.layout.alert_dialog_layout,null);
                builder.setView(view);
                AlertDialog dialog = builder.show();
                

                EditText edLogin = view.findViewById(R.id.ed_login_ad);
            

                builder.setPositiveButton("Yes", new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialog, int which) {
                        AlertDialog alertDialog = (AlertDialog) dialog;
                        EditText edLogin = alertDialog.findViewById(R.id.ed_login_ad);
                    }
                });
            

                    view.setOnClickListener(new View.OnClickListener() {
                        @Override
                        public void onClick(View v) {
                            //action to do
                            v.setBackgroundColor(Color.GREEN);
                        }
                    });
                

                    view.setOnLongClickListener(new View.OnLongClickListener() {
                        @Override
                        public boolean onLongClick(View v) {
                            return true;
                        }
                    });
                

                    view.setOnFocusChangeListener(new View.OnFocusChangeListener() {
                        @Override
                        public void onFocusChange(View v, boolean hasFocus) {
                            if(hasFocus){
                                v.setBackgroundColor(Color.GREEN);
                            }else{
                                v.setBackgroundColor(Color.BLUE);
                            }
                        }
                    });
                

                    editText.addTextChangedListener(new TextWatcher() {
                        @Override
                        public void beforeTextChanged(CharSequence s, int start, int count, int after) {
                        }
                        @Override
                        public void onTextChanged(CharSequence s, int start, int before, int count) {
                        }
                        @Override
                        public void afterTextChanged(Editable s) {
                        }
                    });
                

                    radioButton.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {
                        @Override
                        public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
                        }
                    });
                

                    public class MainActivity extends AppCompactActivity {
                    ...
                    // exemple pour une activité, mais même approche pour une sous classe de View
                    @Override
                    public boolean onTouchEvent(MotionEvent event){
                    
                        int action = MotionEventCompat.getActionMasked(event);
                    
                        switch(action) {
                            case (MotionEvent.ACTION_DOWN) :
                                Log.d(DEBUG_TAG,"Action was DOWN");
                                return true;
                            case (MotionEvent.ACTION_MOVE) :
                                Log.d(DEBUG_TAG,"Action was MOVE");
                                return true;
                            case (MotionEvent.ACTION_UP) :
                                Log.d(DEBUG_TAG,"Action was UP");
                                return true;
                            case (MotionEvent.ACTION_OUTSIDE) :
                                Log.d(DEBUG_TAG,"Movement occurred outside bounds " +
                                        "of current screen element");
                                return true;
                            default :
                                return super.onTouchEvent(event);
                        }
                    }
                    
                    //exemple sur une sous-classe de View
                    View myView = findViewById(R.id.my_view);
                    myView.setOnTouchListener(new OnTouchListener() {
                        public boolean onTouch(View v, MotionEvent event) {
                            //action to do
                            return true;
                        }
                    });
                    
                

                    @Override
                    public boolean onTouchEvent(MotionEvent event) {
                        float xPosition = 0;
                        float yPosition = 0;
                        if(event.getActionMasked() == MotionEvent.ACTION_DOWN){
                            xPosition = event.getX();
                            yPosition = event.getY();
                        }
                        if(event.getActionMasked() == MotionEvent.ACTION_MOVE){
                            xPosition = event.getX();
                            yPosition = event.getY();
                        }
                        return super.onTouchEvent(event);
                    }
                

                    @Override
                    public boolean onTouchEvent(MotionEvent event) {
                        // get pointer index from the event object
                        int pointerIndex = event.getActionIndex();
                        // get pointer ID from pointerIndex
                        int pointerId = event.getPointerId(pointerIndex);
                        // get action
                        int maskedAction = event.getActionMasked();
                        switch (maskedAction) {
                            case MotionEvent.ACTION_DOWN:
                                Log.d(TAG, "index down: " + pointerId);
                                break;
                            case MotionEvent.ACTION_POINTER_DOWN: {
                                Log.d(TAG, "index down: " + pointerId);
                                break;
                            }
                            case MotionEvent.ACTION_MOVE: { // a pointer was moved
                                Log.d(TAG, "index move: " + pointerId);
                                break;
                            }
                            case MotionEvent.ACTION_UP:
                                Log.d(TAG, "index up: " + pointerId);
                
                                break;
                            case MotionEvent.ACTION_POINTER_UP:
                                Log.d(TAG, "index up: " + pointerId);
                                break;
                        }
                
                        return true;
                    }
                

                            public class EventActivity extends AppCompatActivity implements GestureDetector.OnGestureListener {
                                Context context;
                                @Override
                                protected void onCreate(Bundle savedInstanceState) {
                                    super.onCreate(savedInstanceState);
                                    context = this;
                                    setContentView(R.layout.activity_event);
                                }
                                @Override
                                public boolean onDown(MotionEvent e) {
                                    return false;
                                }
                                @Override
                                public void onShowPress(MotionEvent e) {
                                }
                                @Override
                                public boolean onSingleTapUp(MotionEvent e) {
                                    return false;
                                }
                                @Override
                                public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY) {
                                    return false;
                                }
                                @Override
                                public void onLongPress(MotionEvent e) {
                                }
                                @Override
                                public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY) {
                                    return false;
                                }
                            }
                        

                    public class EventActivity extends AppCompatActivity implements GestureDetector.OnGestureListener {
                        private String TAG = "debug-app";
                        GestureDetector gestureDetector;
                        Context context;
                        @Override
                        protected void onCreate(Bundle savedInstanceState) {
                            super.onCreate(savedInstanceState);
                            context = this;
                            setContentView(R.layout.activity_event);
                            gestureDetector = new GestureDetector(this,this);
                        }
                        @Override
                        public boolean onDown(MotionEvent e) {
                            return false;
                        }
                        @Override
                        public void onShowPress(MotionEvent e) {
                        }
                        @Override
                        public boolean onSingleTapUp(MotionEvent e) {
                            return false;
                        }
                        @Override
                        public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY) {
                            return false;
                        }
                        @Override
                        public void onLongPress(MotionEvent e) {
                        }
                        @Override
                        public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY) {
                            return false;
                        }
                    }
                

                    public class EventActivity extends AppCompatActivity implements GestureDetector.OnGestureListener {
                        private String TAG = "debug-app";
                        GestureDetector gestureDetector;
                        Context context;
                        @Override
                        protected void onCreate(Bundle savedInstanceState) {
                            super.onCreate(savedInstanceState);
                            context = this;
                            setContentView(R.layout.activity_event);
                            gestureDetector = new GestureDetector(this,this);
                        }
                        @Override
                        public boolean onTouchEvent(MotionEvent event) {
                            gestureDetector.onTouchEvent(event);
                            return true;
                        }
                        @Override
                        public boolean onDown(MotionEvent e) {
                            return false;
                        }
                        @Override
                        public void onShowPress(MotionEvent e) {
                        }
                        @Override
                        public boolean onSingleTapUp(MotionEvent e) {
                            return false;
                        }
                        @Override
                        public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY) {
                            return false;
                        }
                        @Override
                        public void onLongPress(MotionEvent e) {
                        }
                        @Override
                        public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY) {
                            return false;
                        }
                    }
                

                //si pas besoin de catégoriser les informations
                SharedPreferences sharedPreferences = PreferenceManager.getDefaultSharedPreferences(this);
                //si besoin de catégoriser
                SharedPreferences sharedPreferencesUser = context.getSharedPreferences("user", Context.MODE_PRIVATE);
            

                SharedPreferences sharedPreferences = PreferenceManager.getDefaultSharedPreferences(this);
                String guid = sharedPreferences.getString("id",null);
                int age = sharedPreferences.getInt("age",-1);
            

                SharedPreferences sharedPreferences = PreferenceManager.getDefaultSharedPreferences(this);
                SharedPreferences.Editor editor = sharedPreferences.edit();
                editor.putString("userName", "John Doe");
                editor.putFloat("xPosition", 42.56f);
                editor.putFloat("yPosition", 1056.89f);
                editor.apply();
            

                SharedPreferences sharedPreferences = PreferenceManager.getDefaultSharedPreferences(this);
                SharedPreferences.Editor editor = sharedPreferences.edit();
               
                //suppression par clef
                editor.remove("userName");
                editor.remove("id");
                editor.apply();
               
                //suppression total
                editor.clear();
                editor.apply();
            

            File file = new File(context.getFilesDir(), filename);
            

                String filename = "myFile.txt";
                String fileContents = "Hello world!";
                try (FileOutputStream fos = context.openFileOutput(filename, Context.MODE_PRIVATE)) {
                    fos.write(fileContents.toByteArray());
                }
            

                FileInputStream fileInputStream = context.openFileInput(fileName);
                InputStreamReader inputStreamReader =
                        new InputStreamReader(fileInputStream, StandardCharsets.UTF_8);
                StringBuilder stringBuilder = new StringBuilder();
                try (BufferedReader reader = new BufferedReader(inputStreamReader)) {
                    String line = reader.readLine();
                    while (line != null) {
                        stringBuilder.append(line).append('\n');
                        line = reader.readLine();
                    }
                } catch (IOException e) {
                    // Error occurred when opening raw file for reading.
                } finally {
                    String contents = stringBuilder.toString();
                }
            

                <uses-permission android:name="android.permission.MANAGE_EXTERNAL_STORAGE" />
            

                    File file = new File(Environment.getExternalStorageDirectory().getPath()+ File.separator+ "Android/data"+File.separator + getPackageName() + "/files/"+"myFile.txt" );
                

                CREATE TABLE etudiant (
                    id INTEGER PRIMARY KEY AUTOINCREMENT,
                    first_name TEXT,
                    last_name TEXT,
                    age
                );
            

                public class DataBaseHelper extends SQLiteOpenHelper {
                    public DataBaseHelper(@Nullable Context context, @Nullable String name, @Nullable SQLiteDatabase.CursorFactory factory, int version) {
                        super(context, name, factory, version);
                    }
                    @Override
                    public void onCreate(SQLiteDatabase db) {
                    }
                    @Override
                    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
                    }
                }
            

                @Override
                public void onCreate(SQLiteDatabase db) {
                    db.execSQL("CREATE TABLE etudiant (\n" +
                            "id INTEGER PRIMARY KEY AUTOINCREMENT," +
                            "first_name TEXT," +
                            "last_name TEXT," +
                            "age" +
                            ");");
                    db.execSQL("INSERT INTO etudiant ('first_name','last_name','age') values ('john','doe', 27), ('foo','bar',99);");
                }
                @Override
                public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
                    db.execSQL("DROP TABLE IF EXISTS etudiant");
                    onCreate(db);
                }
            

                public class ConnectionDB {
                    private static int version = 1;
                    private static String bnName = "myBd.db";
                    private static SQLiteDatabase bd = null;
                    private static DataBaseHelper helper;
                    
                    public static SQLiteDatabase getBd(Context context){
                        if(helper == null){
                            helper = new DataBaseHelper(context, bnName, null, version);
                        }
                        bd = helper.getWritableDatabase();
                        return bd;
                    }
                    public static void close(){
                        if(bd!= null &&  !bd.isOpen()){
                            bd.close();
                        }
                    }
                }
            

                    public class EtudiantManager {
                    
                        public static long add(Context context, Etudiant etudiantToAdd){
                            ContentValues contentValues = new ContentValues();
                            contentValues.put("first_name", etudiantToAdd.getFirstName());
                            contentValues.put("last_name", etudiantToAdd.getLastName());
                            contentValues.put("age", etudiantToAdd.getAge());
                            SQLiteDatabase bd = ConnectionDB.getBd(context); //on réutilise ConnctionDB ici
                            return bd.insert("etudiant", null, contentValues);
                        }
                    }
                

                public static void delete(Context context, int idEtudiant){
                    SQLiteDatabase bd = ConnectionDB.getBd(context);
                    bd.delete("etudiant","id = ?" , new String[]{String.valueOf(idEtudiant)});
                }
            

                public int delete (String table,
                                    String whereClause,
                                    String[] whereArgs)
            

                DELETE FROM etudiant WHERE id = ?
            

                DELETE FROM etudiant WHERE id = 7
            

                    DELETE FROM etudiant WHERE id = ? AND name LIKE ?
                

                    public static void update(Context context, Etudiant etudiantToUpdate) {
                        ContentValues contentValues = new ContentValues();
                        contentValues.put("first_name", etudiantToUpdate.getFirstName());
                        contentValues.put("age", etudiantToUpdate.getAge());
                        SQLiteDatabase bd = ConnectionDB.getBd(context);
                        long nbRowChange = bd.update("etudiant", contentValues, "id = ?", new String[]{String.valueOf(etudiantToUpdate.getId())});
                    }
                

                    public static ArrayList<Etudiant> getAll(Context context) {
                        SQLiteDatabase bd = ConnectionDB.getBd(context);
                        String query = "SELECT * FROM etudiant";
                        ArrayList<Etudiant> etudiants = null;
                        Cursor cursor = bd.rawQuery(query, null);
                        if (cursor.isBeforeFirst()) {
                            etudiants = new ArrayList<>();
                            while (cursor.moveToNext()) {
                                Etudiant etudiant = new Etudiant();
                                etudiant.setId(cursor.getInt(cursor.getColumnIndexOrThrow("id")));
                                etudiant.setFirstName(cursor.getString(cursor.getColumnIndexOrThrow("first_name")));
                                etudiant.setLastName(cursor.getString(cursor.getColumnIndexOrThrow("last_name")));
                                etudiant.setAge(cursor.getInt(cursor.getColumnIndexOrThrow("age")));
                                etudiants.add(etudiant);
                            }
                        }
                        return etudiants;
                    }
                

                public static ArrayList<Etudiant> getByAgeLimite(Context context, int ageLimite) {
                    SQLiteDatabase bd = ConnectionDB.getBd(context);
                    String query = "SELECT * FROM etudiant where age > ?";
                    ArrayList<Etudiant> etudiants = null;
                    Cursor cursor = bd.rawQuery(query, new String[]{String.valueOf(ageLimite)});
                    if (cursor.isBeforeFirst()) {
                        etudiants = new ArrayList<>();
                        while (cursor.moveToNext()) {
                            Etudiant etudiant = new Etudiant();
                            etudiant.setId(cursor.getInt(cursor.getColumnIndexOrThrow("id")));
                            etudiant.setFirstName(cursor.getString(cursor.getColumnIndexOrThrow("first_name")));
                            etudiant.setLastName(cursor.getString(cursor.getColumnIndexOrThrow("last_name")));
                            etudiant.setAge(cursor.getInt(cursor.getColumnIndexOrThrow("age")));
                            etudiants.add(etudiant);
                        }
                    }
                    return etudiants;
                }
                

                    SensorManager sensorManager = (SensorManager) getSystemService(Context.SENSOR_SERVICE);
                

                    List<Sensor> sensors = sensorManager.getSensorList(Sensor.TYPE_ALL);
                    for (Sensor sensor : sensors) {
                        Log.d("debug_app", "sensor: " + sensor.getName());
                        Log.d("debug_app", "sensor: " + sensor.getMinDelay());
                        Log.d("debug_app", "sensor: " + sensor.getVersion());
                        Log.d("debug_app", "sensor: " + sensor.getMaximumRange());
                    }
                

                    Sensor sensorLight = sensorManager.getDefaultSensor(Sensor.TYPE_LIGHT);
                    if(sensorLight != null){
                        // sensor existe
                    } else {
                        // prévenir l'utilisateur qu'on ne peut pas continuer
                    }
                

                SensorEventListener sensorEventListener = new SensorEventListener() {
                    @Override
                    public void onSensorChanged(SensorEvent event) {
                    }
                    @Override
                    public void onAccuracyChanged(Sensor sensor, int accuracy) {
                    }
                };
                

                    @Override
                    protected void onResume() {
                        super.onResume();
                        sensorManager.registerListener(sensorEventListener, sensorLight, SensorManager.SENSOR_DELAY_FASTEST);
                    }
                

                    @Override
                    protected void onPause() {
                        super.onPause();
                        sensorManager.unregisterListener(sensorEventListener,sensorLight);
                    }
                

                    public class SensorActivity extends AppCompatActivity {
                        TextView textView;
                        SensorManager sensorManager;
                        SensorEventListener sensorEventListener;
                        Sensor sensorLight;
                        @Override
                        protected void onCreate(Bundle savedInstanceState) {
                            super.onCreate(savedInstanceState);
                            setContentView(R.layout.activity_sensor);
                            textView = findViewById(R.id.text);
                            sensorManager = (SensorManager) getSystemService(Context.SENSOR_SERVICE);
                            sensorLight = sensorManager.getDefaultSensor(Sensor.TYPE_LIGHT);
                            sensorEventListener = new SensorEventListener() {
                                @Override
                                public void onSensorChanged(SensorEvent event) {
                                    float luxValue = event.values[0];
                                    textView.setText(String.valueOf(luxValue) + " lux");
                                }
                                @Override
                                public void onAccuracyChanged(Sensor sensor, int accuracy) {
                                }
                            };
                        }
                        @Override
                        protected void onResume() {
                            super.onResume();
                            sensorManager.registerListener(sensorEventListener, sensorLight, SensorManager.SENSOR_DELAY_FASTEST);
                        }
                        @Override
                        protected void onPause() {
                            super.onPause();
                            sensorManager.unregisterListener(sensorEventListener,sensorLight);
                        }
                    }
                

                    <uses-feature android:name="android.hardware.sensor.accelerometer"
                                  android:required="true" />
                

                    <?xml version="1.0" encoding="utf-8"?>
                    <manifest
                        xmlns:android="http://schemas.android.com/apk/res/android"
                        android:versionCode="1"
                        android:versionName="1.0">
                    
                        <uses-feature android:name="android.hardware.sensor.compass"
                            android:required="true" />
                    
                        <application
                            android:allowBackup="true"
                            android:icon="@mipmap/ic_launcher"
                            android:roundIcon="@mipmap/ic_launcher_round"
                            android:label="@string/app_name"
                            android:supportsRtl="true"
                            android:theme="@style/AppTheme">
                    
                            <activity android:name=".MainActivity">
                                <intent-filter>
                                    <action android:name="android.intent.action.MAIN" />
                                    <category android:name="android.intent.category.LAUNCHER" />
                                </intent-filter>
                            </activity>
                            <activity
                                android:name=".DisplayMessageActivity"
                                android:parentActivityName=".MainActivity" />
                        </application>
                    </manifest>
            

                plugins {
                    id 'com.android.application'
                }
                android {
                    namespace 'com.example.appname'
                    compileSdk 32
                    defaultConfig {
                        applicationId "com.example.appname"
                        minSdk 25
                        targetSdk 32
                        versionCode 1
                        versionName "1.0"
                        testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
                    }
                    buildTypes {
                        release {
                            minifyEnabled false
                            proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
                        }
                    }
                    compileOptions {
                        sourceCompatibility JavaVersion.VERSION_1_8
                        targetCompatibility JavaVersion.VERSION_1_8
                    }
                }
                dependencies {
                    implementation 'androidx.appcompat:appcompat:1.5.1'
                    implementation 'com.google.android.material:material:1.7.0'
                    implementation 'androidx.constraintlayout:constraintlayout:2.1.4'
                    testImplementation 'junit:junit:4.13.2'
                    androidTestImplementation 'androidx.test.ext:junit:1.1.3'
                    androidTestImplementation 'androidx.test.espresso:espresso-core:3.4.0'
                }
            

                    public class MainActivity extends AppCompatActivity {
                        @Override
                        protected void onCreate(Bundle savedInstanceState) {
                            super.onCreate(savedInstanceState);
                            setContentView(R.layout.activity_main);
                        }
                    }
                

                public class MainActivity extends AppCompatActivity {
                    private static final String TAG = "debug_app";
                    @Override
                    protected void onCreate(Bundle savedInstanceState) {
                        super.onCreate(savedInstanceState);
                        setContentView(R.layout.activity_main);
                        Log.d(TAG, "onCreate:");
                    }
                    @Override
                    protected void onStart() {
                        super.onStart();
                        Log.d(TAG, "onStart: ");
                    }
                    @Override
                    protected void onResume() {
                        super.onResume();
                        Log.d(TAG, "onResume: ");
                    }
                    @Override
                    protected void onPause() {
                        super.onPause();
                        Log.d(TAG, "onPause: ");
                    }
                    @Override
                    protected void onStop() {
                        super.onStop();
                        Log.d(TAG, "onStop: ");
                    }
                    @Override
                    protected void onDestroy() {
                        super.onDestroy();
                        Log.d(TAG, "onDestroy: ");
                    }
                }
            

                public class FirstActivity extends Activity {
                }
            

                public class FirstActivity extends AppCompatActivity {
                    @Override
                    protected void onCreate(@Nullable Bundle savedInstanceState) {
                        super.onCreate(savedInstanceState);
                        setContentView(R.layout.activity_first);
                    }
                }
            

                <application
                       ... >
                    <activity android:name=".FirstActivity"
                        android:exported="true">
                        <intent-filter>
                            <action android:name="android.intent.action.MAIN" />
                            <category android:name="android.intent.category.LAUNCHER" />
                        </intent-filter>
                    </activity>
                </application>
            

                <application
                       ... >
                    <activity android:name=".FirstActivity"
                        android:exported="true">
                        <intent-filter>
                            <action android:name="android.intent.action.MAIN" />
                            <category android:name="android.intent.category.LAUNCHER" />
                        </intent-filter>
                    </activity>
                    <activity android:name=".SecondActivité"
                        android:exported="false"/>
                </application>
            

                public class MainActivity extends AppCompatActivity {
                    Context context;
                    @Override
                    protected void onCreate(Bundle savedInstanceState) {
                        super.onCreate(savedInstanceState);
                        context = this; //don t forget this line, else you will have NullPointer
                        setContentView(R.layout.activity_main);
                    }
                }
            

                    android:id="@+id/my_id"
                

                    <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
                            xmlns:app="http://schemas.android.com/apk/res-auto"
                            xmlns:tools="http://schemas.android.com/tools"
                            android:layout_width="match_parent"
                            android:layout_height="match_parent"
                            android:orientation="vertical"
                            tools:context=".MainActivity">
                        <TextView
                                android:layout_width="match_parent"
                                android:layout_height="wrap_content"
                                android:text="Hello World!" />
                        <TextView
                                android:layout_width="wrap_content"
                                android:layout_height="wrap_content"
                                android:layout_gravity="right"
                                android:text="Hello World!" />
                        <TextView
                                android:layout_width="match_parent"
                                android:gravity="right"
                                android:layout_height="wrap_content"
                                android:text="Hello World!" />
                        <TextView
                                android:layout_width="wrap_content"
                                android:layout_height="wrap_content"
                                android:layout_gravity="center"
                                android:text="Hello World!" />
                    </LinearLayout>
                

                    <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
                            xmlns:app="http://schemas.android.com/apk/res-auto"
                            xmlns:tools="http://schemas.android.com/tools"
                            android:layout_width="match_parent"
                            android:layout_height="match_parent"
                            android:orientation="vertical"
                            tools:context=".MainActivity">
                        <Button
                                android:layout_width="match_parent"
                                android:layout_height="0dp"
                                android:layout_weight="40"
                                android:text="btn 1" />
                        <Button
                                android:layout_width="match_parent"
                                android:layout_height="0dp"
                                android:layout_weight="60"
                                android:text="btn 2" />
                    </LinearLayout>
                

                    <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
                            xmlns:app="http://schemas.android.com/apk/res-auto"
                            xmlns:tools="http://schemas.android.com/tools"
                            android:layout_width="match_parent"
                            android:layout_height="match_parent"
                            android:orientation="horizontal"
                            tools:context=".MainActivity">
                        <Button
                                android:layout_width="0dp"
                                android:layout_height="match_parent"
                                android:layout_weight="2"
                                android:text="btn 1" />
                        <Button
                                android:layout_width="0dp"
                                android:layout_height="match_parent"
                                android:layout_weight="5"
                                android:text="btn 2" />
                    </LinearLayout>
                

                    public class MainActivity extends AppCompatActivity {
                        Context context;
                        @Override
                        protected void onCreate(Bundle savedInstanceState) {
                            super.onCreate(savedInstanceState);
                            context = this;
                            //set UI width XML File
                            setContentView(R.layout.activity_main); //we give here reference of XML file
                            
                            //set view width Java File
                            LinearLayout container = new LinearLayout(context);
                            setContentView(container);
                        }
                    }
                

                        <?xml version="1.0" encoding="utf-8"?>
                        <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
                                xmlns:app="http://schemas.android.com/apk/res-auto"
                                xmlns:tools="http://schemas.android.com/tools"
                                android:layout_width="match_parent"
                                android:layout_height="match_parent"
                                android:orientation="vertical"
                                tools:context=".MainActivity">
                            <TextView
                                    android:layout_width="wrap_content"
                                    android:layout_height="wrap_content"
                                    android:text="Hello World!" />
                        </LinearLayout>
                

                    public class MainActivity extends AppCompatActivity {
                        @Override
                        protected void onCreate(Bundle savedInstanceState) {
                            super.onCreate(savedInstanceState);
                            setContentView(R.layout.activity_main);
                        }
                    }
                

                TextView tv = new TextView(this);
                LinearLayout.LayoutParams params = new LinearLayout.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.WRAP_CONTENT);
                tv.setLayoutParams(params);
                

                    public class MainActivity extends AppCompatActivity {
                        Context context;
                        @Override
                        protected void onCreate(Bundle savedInstanceState) {
                            super.onCreate(savedInstanceState);
                            context = this;
                            //create instance of linear layout
                            LinearLayout linearLayoutMain = new LinearLayout(context);
                            linearLayoutMain.setLayoutParams(new LinearLayout.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.MATCH_PARENT));
                            linearLayoutMain.setOrientation(LinearLayout.VERTICAL);
                            //add linearLayout as main container of activity
                            setContentView(linearLayoutMain);
                            //create textview
                            TextView textView = new TextView(context);
                            textView.setText("Hello World!");
                            textView.setLayoutParams(new LinearLayout.LayoutParams(ViewGroup.LayoutParams.WRAP_CONTENT, ViewGroup.LayoutParams.WRAP_CONTENT));
                            //set text view as child of linearlayout
                            linearLayoutMain.addView(textView);
                        }
                    }
                

                    <?xml version="1.0" encoding="utf-8"?>
                    <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
                            xmlns:app="http://schemas.android.com/apk/res-auto"
                            xmlns:tools="http://schemas.android.com/tools"
                            android:layout_width="match_parent"
                            android:layout_height="match_parent"
                            android:orientation="vertical"
                            tools:context=".MainActivity">
                        <TextView
                                android:id="@+id/text_view"
                                android:layout_width="wrap_content"
                                android:layout_height="wrap_content"
                                android:text="Hello World!" />
                    </LinearLayout>
                

                    public class MainActivity extends AppCompatActivity {
                        Context context;
                        @Override
                        protected void onCreate(Bundle savedInstanceState) {
                            super.onCreate(savedInstanceState);
                            context = this;
                            setContentView(R.layout.activity_main);
                            //access to textview
                            TextView textView = findViewById(R.id.text_view);
                            //change value of textview
                            textView.setText("New text to print");
                        }
                    }
                

                    <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
                            android:layout_width="match_parent"
                            android:layout_height="match_parent"
                            android:orientation="horizontal"
                            android:padding="5dp">
                        <TextView
                                android:layout_width="0dp"
                                android:layout_height="wrap_content"
                                android:layout_weight="10"
                                android:background="#f00"
                                android:gravity="center"
                                android:textSize="20dp"
                                android:textColor="#fff"
                                android:text="Left" />
                        <TextView
                                android:layout_width="0dp"
                                android:layout_height="wrap_content"
                                android:layout_weight="10"
                                android:background="#0f0"
                                android:gravity="center"
                                android:textSize="20dp"
                                android:textColor="#fff"
                                android:text="Right" />
                        <TextView
                                android:id="@+id/tv_view_number"
                                android:layout_width="0dp"
                                android:layout_height="wrap_content"
                                android:layout_weight="10"
                                android:background="#00f"
                                android:gravity="center"
                                android:textSize="20dp"
                                android:textColor="#fff"
                                android:text="No " />
                    </LinearLayout>
                

                    public class InflatorActivity extends AppCompatActivity {
                        Context context;
                        @Override
                        protected void onCreate(Bundle savedInstanceState) {
                            super.onCreate(savedInstanceState);
                            context = this;
                            LinearLayout llMain = new LinearLayout(context);
                            llMain.setOrientation(LinearLayout.VERTICAL);
                            setContentView(llMain);
                            for (int i = 0; i < 10; i++) {
                                //deserialization of view
                                LinearLayout linearLayoutSmallView = (LinearLayout) LayoutInflater.from(context).inflate(R.layout.small_view,null);
                                TextView textViewNumberView = linearLayoutSmallView.findViewById(R.id.tv_view_number);
                                textViewNumberView.setText("No : " + (i+1));
                                llMain.addView(linearLayoutSmallView);
                            }
                        }
                    }
                

                Intent intent = new Intent(ctx,ClassName.class);
                startActivity(intent);
            

                            Intent intent = new Intent(this, SecondeActivity.class);
                            intent.putExtra("name","user name");
                            intent.putExtra("id", "456-fesdf-464sdf");
                            intent.putExtra("year", 27);
                            startActivity(intent);
                        

                            Intent intent = getIntent();
                            String nameValue = intent.getStringExtra("name");
                            String idValue = intent.getStringExtra("id");
                            int yearValue =  intent.getIntExtra("year", -1);
                        

                ActivityResultLauncher<Intent> resultActivity = registerForActivityResult(
                        new ActivityResultContracts.StartActivityForResult(),
                        new ActivityResultCallback<ActivityResult>() {
                            @Override
                            public void onActivityResult(ActivityResult result) {
                                if (result.getResultCode() == RESULT_OK) {
                                    //do instruction when result
                                    Intent intent = result.getData();
                                    String dataString = intent.getStringExtra("dataKey");
                                }
                            }
                        }
                );
                Intent intent = new Intent(this, SecondeActivity.class);
                resultActivity.launch(intent);
            

                button.setOnClickListener(new View.OnClickListener() {
                    @Override
                    public void onClick(View v) {
                        Intent intent = new Intent();
                        intent.putExtra("dataKey","hello data"); //1
                        setResult(RESULT_OK, intent); //2
                        finish(); //3
                    }
                });
            

                    MyProject/
                        src/
                            MyActivity.java
                        res/
                            drawable/
                                graphic.png
                            layout/
                                main.xml
                                info.xml
                            mipmap/
                                icon.png
                            values/
                                strings.xml
                

                    public class R {
                        public static class layout{
                            public static final int activity_main = 0xabc123;
                            public static final int my_layout = 0xabc124;
                            public static final int other_layout = 0xabc125;
                        }
                        public static class drawable{
                            public static final int image1 = 0xbcd123;
                            public static final int image2 = 0xbcd124;
                            public static final int chat = 0xbcd125;
                        }
                        public static class string{
                            public static final int msg_welcom = 0xefa123;
                            public static final int app_name = 0xefa124;
                            public static final int msg_btn_send = 0xefa125;
                        }
                        public static class color{
                            public static final int color_texte = 0x456fa12;
                            public static final int color_btn = 0x456fa13;
                            public static final int color_border = 0x456fa14;
                            public static final int color_title = 0x456fa15;
                        }
                    }
                

                    Resources resources = context.getResources();
                    String stringRessource = resources.getString(R.string.key_ressource);
                    
                    //XXX resValue = resources.getXXX(id);
                

                    @[package:]type_ressource/nom_ressource
                

                    @+[package:]type/nom
                

                    <string name="dyn1">Hello %1$s, you have %2$d years</string>
                

                    Resources res = context.getResources();
                    String chaine = res.getString(R.string.dyn1, "durand", 32);
                

                    AssetManager assetManager = getAssets(); //into activity
                    AssetManager assetManager = context.getAssets(); // everywhere in application
                    try {
                        InputStream inputStream = assetManager.open("fileName");
                    } catch (IOException e) {
                        throw new RuntimeException(e);
                    }
                

                    InputStream inputStream = assetManager.open("fileName");
                    Drawable drawableImage = Drawable.createFromStream(inputStream, null);
                    Bitmap bitmapImage = BitmapFactory.decodeStream(inputStream);
                

                                <menu xmlns:android="http://schemas.android.com/apk/res/android"
                                    xmlns:app="http://schemas.android.com/apk/res-auto">
                                <item
                                        android:id="@+id/menu_play"
                                        android:icon="@android:drawable/ic_media_play"
                                        android:title="play"
                                        app:showAsAction="always" />
                                <item
                                        android:id="@+id/menu_stop"
                                        android:icon="@android:drawable/ic_media_stop"
                                        android:title="stop"
                                        app:showAsAction="always" />
                                <item
                                        android:id="@+id/menu_next"
                                        android:title="next"
                                        app:showAsAction="always" />
                                <item
                                        android:id="@+id/menu_pause"
                                        android:icon="@android:drawable/ic_media_pause"
                                        android:title="pause"
                                        app:showAsAction="ifRoom" />
                                <item
                                        android:id="@+id/menu_reset"
                                        android:title="reset"
                                        app:showAsAction="never" />
                            </menu>
                            

                @Override
                public boolean onCreateOptionsMenu(Menu menu) {
                    MenuInflater menuInflater = getMenuInflater();
                    menuInflater.inflate(R.menu.layout_menu, menu);
                    return true;
                }
            

                @Override
                public boolean onCreateOptionsMenu(Menu menu) {
                    int idItem = 1;        // exemple pour ajouter un item
                    int order = 1;
                    MenuItem menuItem = menu.add(0, idItem, order, "mon menu");
                    return true;
                }
            

                @Override
                public boolean onOptionsItemSelected(@NonNull MenuItem item) {
                    boolean retour = super.onOptionsItemSelected(item);
                    switch (item.getItemId()) {
                        case R.id.menu_play:
                            //action todo
                            retour = true;
                            break;
                        case R.id.menu_stop:
                            //action todo
                            retour = true;
                            break;
                        case R.id.menu_pause:
                            //action todo
                            retour = true;
                            break;
                        case R.id.menu_next:
                            //action todo
                            retour = true;
                            break;
                        case R.id.menu_reset:
                            //action todo
                            retour = true;
                            break;
                    }
                    return retour;
                }
            

                AlertDialog.Builder builder = new AlertDialog.Builder(context);
                builder.setTitle("my wonderful title");
                builder.setMessage("my beautiful Message to print ");
                AlertDialog dialog = builder.create();
                dialog.show();
                //or
                AlertDialog dialog = builder.show();
            

                AlertDialog.Builder builder = new AlertDialog.Builder(context);
                builder.setTitle("my wonderful title");
                builder.setMessage("my beautiful Message to print ");
                builder.setPositiveButton("Yes", new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialog, int which) {
                        //action if yes is select
                    }
                });
                builder.setNeutralButton("i don't know", new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialog, int which) {
                        //action if i don't know is select
                    }
                });
                builder.setPositiveButton("no", new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialog, int which) {
                        //action if no select
                    }
                });
                AlertDialog dialog = builder.show();
            

                String[] items = new String[]{"orange","blue","green"};
                AlertDialog.Builder builder = new AlertDialog.Builder(context);
                builder.setTitle("my wonderful title");
                builder.setItems(items, new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialog, int which) {
                        String value = items[which];//which = position of item select
                    }
                });
                AlertDialog dialog = builder.show();
            

                <string-array name="colors_list">
                    <item>orange</item>
                    <item>blue</item>
                    <item>green</item>
                </string-array>
            

                builder.setItems(R.array.colors_list, new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialog, int which) {
                        String[] items = getResources().getStringArray(R.array.colors_list); //pour récupérer les données depuis le répertoire Ressource
                        String value = items[which];//which = position of item select
                    }
                });
            

vue définie en xml

                <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
                        android:layout_width="match_parent"
                        android:layout_height="match_parent"
                        android:orientation="vertical">
                    <LinearLayout
                            android:layout_width="match_parent"
                            android:layout_height="wrap_content"
                            android:orientation="horizontal">
                        <TextView
                                android:layout_width="0px"
                                android:layout_height="wrap_content"
                                android:layout_weight="30"
                                android:text="login : " />
                        <EditText
                                android:id="@+id/ed_login_ad"
                                android:layout_width="0px"
                                android:layout_height="wrap_content"
                                android:layout_weight="70" />
                    </LinearLayout>
                    <LinearLayout
                            android:layout_width="match_parent"
                            android:layout_height="wrap_content"
                            android:orientation="horizontal">
                        <TextView
                                android:layout_width="0px"
                                android:layout_height="wrap_content"
                                android:layout_weight="30"
                                android:text="password : " />
                        <EditText
                                android:id="@+id/ed_password_ad"
                                android:layout_width="0px"
                                android:layout_height="wrap_content"
                                android:layout_weight="70" />
                    </LinearLayout>
                </LinearLayout>
            

code java pour un alert dialog avec une vue perso

                AlertDialog.Builder builder = new AlertDialog.Builder(context);
                builder.setTitle("my wonderful title");
                View view = LayoutInflater.from(context).inflate(R.layout.alert_dialog_layout,null);
                builder.setView(view);
                AlertDialog dialog = builder.show();
                

                EditText edLogin = view.findViewById(R.id.ed_login_ad);
            

                builder.setPositiveButton("Yes", new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialog, int which) {
                        AlertDialog alertDialog = (AlertDialog) dialog;
                        EditText edLogin = alertDialog.findViewById(R.id.ed_login_ad);
                    }
                });
            

                    view.setOnClickListener(new View.OnClickListener() {
                        @Override
                        public void onClick(View v) {
                            //action to do
                            v.setBackgroundColor(Color.GREEN);
                        }
                    });
                

                    view.setOnLongClickListener(new View.OnLongClickListener() {
                        @Override
                        public boolean onLongClick(View v) {
                            return true;
                        }
                    });
                

                    view.setOnFocusChangeListener(new View.OnFocusChangeListener() {
                        @Override
                        public void onFocusChange(View v, boolean hasFocus) {
                            if(hasFocus){
                                v.setBackgroundColor(Color.GREEN);
                            }else{
                                v.setBackgroundColor(Color.BLUE);
                            }
                        }
                    });
                

                    editText.addTextChangedListener(new TextWatcher() {
                        @Override
                        public void beforeTextChanged(CharSequence s, int start, int count, int after) {
                        }
                        @Override
                        public void onTextChanged(CharSequence s, int start, int before, int count) {
                        }
                        @Override
                        public void afterTextChanged(Editable s) {
                        }
                    });
                

                    radioButton.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {
                        @Override
                        public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
                        }
                    });
                

                    public class MainActivity extends AppCompactActivity {
                    ...
                    // exemple pour une activité, mais même approche pour une sous classe de View
                    @Override
                    public boolean onTouchEvent(MotionEvent event){
                    
                        int action = MotionEventCompat.getActionMasked(event);
                    
                        switch(action) {
                            case (MotionEvent.ACTION_DOWN) :
                                Log.d(DEBUG_TAG,"Action was DOWN");
                                return true;
                            case (MotionEvent.ACTION_MOVE) :
                                Log.d(DEBUG_TAG,"Action was MOVE");
                                return true;
                            case (MotionEvent.ACTION_UP) :
                                Log.d(DEBUG_TAG,"Action was UP");
                                return true;
                            case (MotionEvent.ACTION_OUTSIDE) :
                                Log.d(DEBUG_TAG,"Movement occurred outside bounds " +
                                        "of current screen element");
                                return true;
                            default :
                                return super.onTouchEvent(event);
                        }
                    }
                    
                    //exemple sur une sous-classe de View
                    View myView = findViewById(R.id.my_view);
                    myView.setOnTouchListener(new OnTouchListener() {
                        public boolean onTouch(View v, MotionEvent event) {
                            //action to do
                            return true;
                        }
                    });
                    
                

                    @Override
                    public boolean onTouchEvent(MotionEvent event) {
                        float xPosition = 0;
                        float yPosition = 0;
                        if(event.getActionMasked() == MotionEvent.ACTION_DOWN){
                            xPosition = event.getX();
                            yPosition = event.getY();
                        }
                        if(event.getActionMasked() == MotionEvent.ACTION_MOVE){
                            xPosition = event.getX();
                            yPosition = event.getY();
                        }
                        return super.onTouchEvent(event);
                    }
                

                    @Override
                    public boolean onTouchEvent(MotionEvent event) {
                        // get pointer index from the event object
                        int pointerIndex = event.getActionIndex();
                        // get pointer ID from pointerIndex
                        int pointerId = event.getPointerId(pointerIndex);
                        // get action
                        int maskedAction = event.getActionMasked();
                        switch (maskedAction) {
                            case MotionEvent.ACTION_DOWN:
                                Log.d(TAG, "index down: " + pointerId);
                                break;
                            case MotionEvent.ACTION_POINTER_DOWN: {
                                Log.d(TAG, "index down: " + pointerId);
                                break;
                            }
                            case MotionEvent.ACTION_MOVE: { // a pointer was moved
                                Log.d(TAG, "index move: " + pointerId);
                                break;
                            }
                            case MotionEvent.ACTION_UP:
                                Log.d(TAG, "index up: " + pointerId);
                
                                break;
                            case MotionEvent.ACTION_POINTER_UP:
                                Log.d(TAG, "index up: " + pointerId);
                                break;
                        }
                
                        return true;
                    }
                

                            public class EventActivity extends AppCompatActivity implements GestureDetector.OnGestureListener {
                                Context context;
                                @Override
                                protected void onCreate(Bundle savedInstanceState) {
                                    super.onCreate(savedInstanceState);
                                    context = this;
                                    setContentView(R.layout.activity_event);
                                }
                                @Override
                                public boolean onDown(MotionEvent e) {
                                    return false;
                                }
                                @Override
                                public void onShowPress(MotionEvent e) {
                                }
                                @Override
                                public boolean onSingleTapUp(MotionEvent e) {
                                    return false;
                                }
                                @Override
                                public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY) {
                                    return false;
                                }
                                @Override
                                public void onLongPress(MotionEvent e) {
                                }
                                @Override
                                public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY) {
                                    return false;
                                }
                            }
                        

                    public class EventActivity extends AppCompatActivity implements GestureDetector.OnGestureListener {
                        private String TAG = "debug-app";
                        GestureDetector gestureDetector;
                        Context context;
                        @Override
                        protected void onCreate(Bundle savedInstanceState) {
                            super.onCreate(savedInstanceState);
                            context = this;
                            setContentView(R.layout.activity_event);
                            gestureDetector = new GestureDetector(this,this);
                        }
                        @Override
                        public boolean onDown(MotionEvent e) {
                            return false;
                        }
                        @Override
                        public void onShowPress(MotionEvent e) {
                        }
                        @Override
                        public boolean onSingleTapUp(MotionEvent e) {
                            return false;
                        }
                        @Override
                        public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY) {
                            return false;
                        }
                        @Override
                        public void onLongPress(MotionEvent e) {
                        }
                        @Override
                        public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY) {
                            return false;
                        }
                    }
                

                    public class EventActivity extends AppCompatActivity implements GestureDetector.OnGestureListener {
                        private String TAG = "debug-app";
                        GestureDetector gestureDetector;
                        Context context;
                        @Override
                        protected void onCreate(Bundle savedInstanceState) {
                            super.onCreate(savedInstanceState);
                            context = this;
                            setContentView(R.layout.activity_event);
                            gestureDetector = new GestureDetector(this,this);
                        }
                        @Override
                        public boolean onTouchEvent(MotionEvent event) {
                            gestureDetector.onTouchEvent(event);
                            return true;
                        }
                        @Override
                        public boolean onDown(MotionEvent e) {
                            return false;
                        }
                        @Override
                        public void onShowPress(MotionEvent e) {
                        }
                        @Override
                        public boolean onSingleTapUp(MotionEvent e) {
                            return false;
                        }
                        @Override
                        public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY) {
                            return false;
                        }
                        @Override
                        public void onLongPress(MotionEvent e) {
                        }
                        @Override
                        public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY) {
                            return false;
                        }
                    }
                

                //si pas besoin de catégoriser les informations
                SharedPreferences sharedPreferences = PreferenceManager.getDefaultSharedPreferences(this);
                //si besoin de catégoriser
                SharedPreferences sharedPreferencesUser = context.getSharedPreferences("user", Context.MODE_PRIVATE);
            

                SharedPreferences sharedPreferences = PreferenceManager.getDefaultSharedPreferences(this);
                String guid = sharedPreferences.getString("id",null);
                int age = sharedPreferences.getInt("age",-1);
            

                SharedPreferences sharedPreferences = PreferenceManager.getDefaultSharedPreferences(this);
                SharedPreferences.Editor editor = sharedPreferences.edit();
                editor.putString("userName", "John Doe");
                editor.putFloat("xPosition", 42.56f);
                editor.putFloat("yPosition", 1056.89f);
                editor.apply();
            

                SharedPreferences sharedPreferences = PreferenceManager.getDefaultSharedPreferences(this);
                SharedPreferences.Editor editor = sharedPreferences.edit();
               
                //suppression par clef
                editor.remove("userName");
                editor.remove("id");
                editor.apply();
               
                //suppression total
                editor.clear();
                editor.apply();
            

            File file = new File(context.getFilesDir(), filename);
            

                String filename = "myFile.txt";
                String fileContents = "Hello world!";
                try (FileOutputStream fos = context.openFileOutput(filename, Context.MODE_PRIVATE)) {
                    fos.write(fileContents.toByteArray());
                }
            

                FileInputStream fileInputStream = context.openFileInput(fileName);
                InputStreamReader inputStreamReader =
                        new InputStreamReader(fileInputStream, StandardCharsets.UTF_8);
                StringBuilder stringBuilder = new StringBuilder();
                try (BufferedReader reader = new BufferedReader(inputStreamReader)) {
                    String line = reader.readLine();
                    while (line != null) {
                        stringBuilder.append(line).append('\n');
                        line = reader.readLine();
                    }
                } catch (IOException e) {
                    // Error occurred when opening raw file for reading.
                } finally {
                    String contents = stringBuilder.toString();
                }
            

                <uses-permission android:name="android.permission.MANAGE_EXTERNAL_STORAGE" />
            

                    File file = new File(Environment.getExternalStorageDirectory().getPath()+ File.separator+ "Android/data"+File.separator + getPackageName() + "/files/"+"myFile.txt" );
                

                CREATE TABLE etudiant (
                    id INTEGER PRIMARY KEY AUTOINCREMENT,
                    first_name TEXT,
                    last_name TEXT,
                    age
                );
            

                public class DataBaseHelper extends SQLiteOpenHelper {
                    public DataBaseHelper(@Nullable Context context, @Nullable String name, @Nullable SQLiteDatabase.CursorFactory factory, int version) {
                        super(context, name, factory, version);
                    }
                    @Override
                    public void onCreate(SQLiteDatabase db) {
                    }
                    @Override
                    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
                    }
                }
            

                @Override
                public void onCreate(SQLiteDatabase db) {
                    db.execSQL("CREATE TABLE etudiant (\n" +
                            "id INTEGER PRIMARY KEY AUTOINCREMENT," +
                            "first_name TEXT," +
                            "last_name TEXT," +
                            "age" +
                            ");");
                    db.execSQL("INSERT INTO etudiant ('first_name','last_name','age') values ('john','doe', 27), ('foo','bar',99);");
                }
                @Override
                public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
                    db.execSQL("DROP TABLE IF EXISTS etudiant");
                    onCreate(db);
                }
            

                public class ConnectionDB {
                    private static int version = 1;
                    private static String bnName = "myBd.db";
                    private static SQLiteDatabase bd = null;
                    private static DataBaseHelper helper;
                    
                    public static SQLiteDatabase getBd(Context context){
                        if(helper == null){
                            helper = new DataBaseHelper(context, bnName, null, version);
                        }
                        bd = helper.getWritableDatabase();
                        return bd;
                    }
                    public static void close(){
                        if(bd!= null &&  !bd.isOpen()){
                            bd.close();
                        }
                    }
                }
            

                    public class EtudiantManager {
                    
                        public static long add(Context context, Etudiant etudiantToAdd){
                            ContentValues contentValues = new ContentValues();
                            contentValues.put("first_name", etudiantToAdd.getFirstName());
                            contentValues.put("last_name", etudiantToAdd.getLastName());
                            contentValues.put("age", etudiantToAdd.getAge());
                            SQLiteDatabase bd = ConnectionDB.getBd(context); //on réutilise ConnctionDB ici
                            return bd.insert("etudiant", null, contentValues);
                        }
                    }
                

                public static void delete(Context context, int idEtudiant){
                    SQLiteDatabase bd = ConnectionDB.getBd(context);
                    bd.delete("etudiant","id = ?" , new String[]{String.valueOf(idEtudiant)});
                }
            

                public int delete (String table,
                                    String whereClause,
                                    String[] whereArgs)
            

                DELETE FROM etudiant WHERE id = ?
            

                DELETE FROM etudiant WHERE id = 7
            

                    DELETE FROM etudiant WHERE id = ? AND name LIKE ?
                

                    public static void update(Context context, Etudiant etudiantToUpdate) {
                        ContentValues contentValues = new ContentValues();
                        contentValues.put("first_name", etudiantToUpdate.getFirstName());
                        contentValues.put("age", etudiantToUpdate.getAge());
                        SQLiteDatabase bd = ConnectionDB.getBd(context);
                        long nbRowChange = bd.update("etudiant", contentValues, "id = ?", new String[]{String.valueOf(etudiantToUpdate.getId())});
                    }
                

                    public static ArrayList<Etudiant> getAll(Context context) {
                        SQLiteDatabase bd = ConnectionDB.getBd(context);
                        String query = "SELECT * FROM etudiant";
                        ArrayList<Etudiant> etudiants = null;
                        Cursor cursor = bd.rawQuery(query, null);
                        if (cursor.isBeforeFirst()) {
                            etudiants = new ArrayList<>();
                            while (cursor.moveToNext()) {
                                Etudiant etudiant = new Etudiant();
                                etudiant.setId(cursor.getInt(cursor.getColumnIndexOrThrow("id")));
                                etudiant.setFirstName(cursor.getString(cursor.getColumnIndexOrThrow("first_name")));
                                etudiant.setLastName(cursor.getString(cursor.getColumnIndexOrThrow("last_name")));
                                etudiant.setAge(cursor.getInt(cursor.getColumnIndexOrThrow("age")));
                                etudiants.add(etudiant);
                            }
                        }
                        return etudiants;
                    }
                

                public static ArrayList<Etudiant> getByAgeLimite(Context context, int ageLimite) {
                    SQLiteDatabase bd = ConnectionDB.getBd(context);
                    String query = "SELECT * FROM etudiant where age > ?";
                    ArrayList<Etudiant> etudiants = null;
                    Cursor cursor = bd.rawQuery(query, new String[]{String.valueOf(ageLimite)});
                    if (cursor.isBeforeFirst()) {
                        etudiants = new ArrayList<>();
                        while (cursor.moveToNext()) {
                            Etudiant etudiant = new Etudiant();
                            etudiant.setId(cursor.getInt(cursor.getColumnIndexOrThrow("id")));
                            etudiant.setFirstName(cursor.getString(cursor.getColumnIndexOrThrow("first_name")));
                            etudiant.setLastName(cursor.getString(cursor.getColumnIndexOrThrow("last_name")));
                            etudiant.setAge(cursor.getInt(cursor.getColumnIndexOrThrow("age")));
                            etudiants.add(etudiant);
                        }
                    }
                    return etudiants;
                }
                

                    SensorManager sensorManager = (SensorManager) getSystemService(Context.SENSOR_SERVICE);
                

                    List<Sensor> sensors = sensorManager.getSensorList(Sensor.TYPE_ALL);
                    for (Sensor sensor : sensors) {
                        Log.d("debug_app", "sensor: " + sensor.getName());
                        Log.d("debug_app", "sensor: " + sensor.getMinDelay());
                        Log.d("debug_app", "sensor: " + sensor.getVersion());
                        Log.d("debug_app", "sensor: " + sensor.getMaximumRange());
                    }
                

                    Sensor sensorLight = sensorManager.getDefaultSensor(Sensor.TYPE_LIGHT);
                    if(sensorLight != null){
                        // sensor existe
                    } else {
                        // prévenir l'utilisateur qu'on ne peut pas continuer
                    }
                

                SensorEventListener sensorEventListener = new SensorEventListener() {
                    @Override
                    public void onSensorChanged(SensorEvent event) {
                    }
                    @Override
                    public void onAccuracyChanged(Sensor sensor, int accuracy) {
                    }
                };
                

                    @Override
                    protected void onResume() {
                        super.onResume();
                        sensorManager.registerListener(sensorEventListener, sensorLight, SensorManager.SENSOR_DELAY_FASTEST);
                    }
                

                    @Override
                    protected void onPause() {
                        super.onPause();
                        sensorManager.unregisterListener(sensorEventListener,sensorLight);
                    }
                

                    public class SensorActivity extends AppCompatActivity {
                        TextView textView;
                        SensorManager sensorManager;
                        SensorEventListener sensorEventListener;
                        Sensor sensorLight;
                        @Override
                        protected void onCreate(Bundle savedInstanceState) {
                            super.onCreate(savedInstanceState);
                            setContentView(R.layout.activity_sensor);
                            textView = findViewById(R.id.text);
                            sensorManager = (SensorManager) getSystemService(Context.SENSOR_SERVICE);
                            sensorLight = sensorManager.getDefaultSensor(Sensor.TYPE_LIGHT);
                            sensorEventListener = new SensorEventListener() {
                                @Override
                                public void onSensorChanged(SensorEvent event) {
                                    float luxValue = event.values[0];
                                    textView.setText(String.valueOf(luxValue) + " lux");
                                }
                                @Override
                                public void onAccuracyChanged(Sensor sensor, int accuracy) {
                                }
                            };
                        }
                        @Override
                        protected void onResume() {
                            super.onResume();
                            sensorManager.registerListener(sensorEventListener, sensorLight, SensorManager.SENSOR_DELAY_FASTEST);
                        }
                        @Override
                        protected void onPause() {
                            super.onPause();
                            sensorManager.unregisterListener(sensorEventListener,sensorLight);
                        }
                    }
                

                    <uses-feature android:name="android.hardware.sensor.accelerometer"
                                  android:required="true" />
                

                    <?xml version="1.0" encoding="utf-8"?>
                    <manifest
                        xmlns:android="http://schemas.android.com/apk/res/android"
                        android:versionCode="1"
                        android:versionName="1.0">
                    
                        <uses-feature android:name="android.hardware.sensor.compass"
                            android:required="true" />
                    
                        <application
                            android:allowBackup="true"
                            android:icon="@mipmap/ic_launcher"
                            android:roundIcon="@mipmap/ic_launcher_round"
                            android:label="@string/app_name"
                            android:supportsRtl="true"
                            android:theme="@style/AppTheme">
                    
                            <activity android:name=".MainActivity">
                                <intent-filter>
                                    <action android:name="android.intent.action.MAIN" />
                                    <category android:name="android.intent.category.LAUNCHER" />
                                </intent-filter>
                            </activity>
                            <activity
                                android:name=".DisplayMessageActivity"
                                android:parentActivityName=".MainActivity" />
                        </application>
                    </manifest>
            

                plugins {
                    id 'com.android.application'
                }
                android {
                    namespace 'com.example.appname'
                    compileSdk 32
                    defaultConfig {
                        applicationId "com.example.appname"
                        minSdk 25
                        targetSdk 32
                        versionCode 1
                        versionName "1.0"
                        testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
                    }
                    buildTypes {
                        release {
                            minifyEnabled false
                            proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
                        }
                    }
                    compileOptions {
                        sourceCompatibility JavaVersion.VERSION_1_8
                        targetCompatibility JavaVersion.VERSION_1_8
                    }
                }
                dependencies {
                    implementation 'androidx.appcompat:appcompat:1.5.1'
                    implementation 'com.google.android.material:material:1.7.0'
                    implementation 'androidx.constraintlayout:constraintlayout:2.1.4'
                    testImplementation 'junit:junit:4.13.2'
                    androidTestImplementation 'androidx.test.ext:junit:1.1.3'
                    androidTestImplementation 'androidx.test.espresso:espresso-core:3.4.0'
                }
            

                    public class MainActivity extends AppCompatActivity {
                        @Override
                        protected void onCreate(Bundle savedInstanceState) {
                            super.onCreate(savedInstanceState);
                            setContentView(R.layout.activity_main);
                        }
                    }
                

                public class MainActivity extends AppCompatActivity {
                    private static final String TAG = "debug_app";
                    @Override
                    protected void onCreate(Bundle savedInstanceState) {
                        super.onCreate(savedInstanceState);
                        setContentView(R.layout.activity_main);
                        Log.d(TAG, "onCreate:");
                    }
                    @Override
                    protected void onStart() {
                        super.onStart();
                        Log.d(TAG, "onStart: ");
                    }
                    @Override
                    protected void onResume() {
                        super.onResume();
                        Log.d(TAG, "onResume: ");
                    }
                    @Override
                    protected void onPause() {
                        super.onPause();
                        Log.d(TAG, "onPause: ");
                    }
                    @Override
                    protected void onStop() {
                        super.onStop();
                        Log.d(TAG, "onStop: ");
                    }
                    @Override
                    protected void onDestroy() {
                        super.onDestroy();
                        Log.d(TAG, "onDestroy: ");
                    }
                }
            

                public class FirstActivity extends Activity {
                }
            

                public class FirstActivity extends AppCompatActivity {
                    @Override
                    protected void onCreate(@Nullable Bundle savedInstanceState) {
                        super.onCreate(savedInstanceState);
                        setContentView(R.layout.activity_first);
                    }
                }
            

                <application
                       ... >
                    <activity android:name=".FirstActivity"
                        android:exported="true">
                        <intent-filter>
                            <action android:name="android.intent.action.MAIN" />
                            <category android:name="android.intent.category.LAUNCHER" />
                        </intent-filter>
                    </activity>
                </application>
            

                <application
                       ... >
                    <activity android:name=".FirstActivity"
                        android:exported="true">
                        <intent-filter>
                            <action android:name="android.intent.action.MAIN" />
                            <category android:name="android.intent.category.LAUNCHER" />
                        </intent-filter>
                    </activity>
                    <activity android:name=".SecondActivité"
                        android:exported="false"/>
                </application>
            

                public class MainActivity extends AppCompatActivity {
                    Context context;
                    @Override
                    protected void onCreate(Bundle savedInstanceState) {
                        super.onCreate(savedInstanceState);
                        context = this; //don t forget this line, else you will have NullPointer
                        setContentView(R.layout.activity_main);
                    }
                }
            

                    android:id="@+id/my_id"
                

                    <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
                            xmlns:app="http://schemas.android.com/apk/res-auto"
                            xmlns:tools="http://schemas.android.com/tools"
                            android:layout_width="match_parent"
                            android:layout_height="match_parent"
                            android:orientation="vertical"
                            tools:context=".MainActivity">
                        <TextView
                                android:layout_width="match_parent"
                                android:layout_height="wrap_content"
                                android:text="Hello World!" />
                        <TextView
                                android:layout_width="wrap_content"
                                android:layout_height="wrap_content"
                                android:layout_gravity="right"
                                android:text="Hello World!" />
                        <TextView
                                android:layout_width="match_parent"
                                android:gravity="right"
                                android:layout_height="wrap_content"
                                android:text="Hello World!" />
                        <TextView
                                android:layout_width="wrap_content"
                                android:layout_height="wrap_content"
                                android:layout_gravity="center"
                                android:text="Hello World!" />
                    </LinearLayout>
                

                    <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
                            xmlns:app="http://schemas.android.com/apk/res-auto"
                            xmlns:tools="http://schemas.android.com/tools"
                            android:layout_width="match_parent"
                            android:layout_height="match_parent"
                            android:orientation="vertical"
                            tools:context=".MainActivity">
                        <Button
                                android:layout_width="match_parent"
                                android:layout_height="0dp"
                                android:layout_weight="40"
                                android:text="btn 1" />
                        <Button
                                android:layout_width="match_parent"
                                android:layout_height="0dp"
                                android:layout_weight="60"
                                android:text="btn 2" />
                    </LinearLayout>
                

                    <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
                            xmlns:app="http://schemas.android.com/apk/res-auto"
                            xmlns:tools="http://schemas.android.com/tools"
                            android:layout_width="match_parent"
                            android:layout_height="match_parent"
                            android:orientation="horizontal"
                            tools:context=".MainActivity">
                        <Button
                                android:layout_width="0dp"
                                android:layout_height="match_parent"
                                android:layout_weight="2"
                                android:text="btn 1" />
                        <Button
                                android:layout_width="0dp"
                                android:layout_height="match_parent"
                                android:layout_weight="5"
                                android:text="btn 2" />
                    </LinearLayout>
                

                    public class MainActivity extends AppCompatActivity {
                        Context context;
                        @Override
                        protected void onCreate(Bundle savedInstanceState) {
                            super.onCreate(savedInstanceState);
                            context = this;
                            //set UI width XML File
                            setContentView(R.layout.activity_main); //we give here reference of XML file
                            
                            //set view width Java File
                            LinearLayout container = new LinearLayout(context);
                            setContentView(container);
                        }
                    }
                

                        <?xml version="1.0" encoding="utf-8"?>
                        <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
                                xmlns:app="http://schemas.android.com/apk/res-auto"
                                xmlns:tools="http://schemas.android.com/tools"
                                android:layout_width="match_parent"
                                android:layout_height="match_parent"
                                android:orientation="vertical"
                                tools:context=".MainActivity">
                            <TextView
                                    android:layout_width="wrap_content"
                                    android:layout_height="wrap_content"
                                    android:text="Hello World!" />
                        </LinearLayout>
                

                    public class MainActivity extends AppCompatActivity {
                        @Override
                        protected void onCreate(Bundle savedInstanceState) {
                            super.onCreate(savedInstanceState);
                            setContentView(R.layout.activity_main);
                        }
                    }
                

                TextView tv = new TextView(this);
                LinearLayout.LayoutParams params = new LinearLayout.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.WRAP_CONTENT);
                tv.setLayoutParams(params);
                

                    public class MainActivity extends AppCompatActivity {
                        Context context;
                        @Override
                        protected void onCreate(Bundle savedInstanceState) {
                            super.onCreate(savedInstanceState);
                            context = this;
                            //create instance of linear layout
                            LinearLayout linearLayoutMain = new LinearLayout(context);
                            linearLayoutMain.setLayoutParams(new LinearLayout.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.MATCH_PARENT));
                            linearLayoutMain.setOrientation(LinearLayout.VERTICAL);
                            //add linearLayout as main container of activity
                            setContentView(linearLayoutMain);
                            //create textview
                            TextView textView = new TextView(context);
                            textView.setText("Hello World!");
                            textView.setLayoutParams(new LinearLayout.LayoutParams(ViewGroup.LayoutParams.WRAP_CONTENT, ViewGroup.LayoutParams.WRAP_CONTENT));
                            //set text view as child of linearlayout
                            linearLayoutMain.addView(textView);
                        }
                    }
                

                    <?xml version="1.0" encoding="utf-8"?>
                    <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
                            xmlns:app="http://schemas.android.com/apk/res-auto"
                            xmlns:tools="http://schemas.android.com/tools"
                            android:layout_width="match_parent"
                            android:layout_height="match_parent"
                            android:orientation="vertical"
                            tools:context=".MainActivity">
                        <TextView
                                android:id="@+id/text_view"
                                android:layout_width="wrap_content"
                                android:layout_height="wrap_content"
                                android:text="Hello World!" />
                    </LinearLayout>
                

                    public class MainActivity extends AppCompatActivity {
                        Context context;
                        @Override
                        protected void onCreate(Bundle savedInstanceState) {
                            super.onCreate(savedInstanceState);
                            context = this;
                            setContentView(R.layout.activity_main);
                            //access to textview
                            TextView textView = findViewById(R.id.text_view);
                            //change value of textview
                            textView.setText("New text to print");
                        }
                    }
                

                    <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
                            android:layout_width="match_parent"
                            android:layout_height="match_parent"
                            android:orientation="horizontal"
                            android:padding="5dp">
                        <TextView
                                android:layout_width="0dp"
                                android:layout_height="wrap_content"
                                android:layout_weight="10"
                                android:background="#f00"
                                android:gravity="center"
                                android:textSize="20dp"
                                android:textColor="#fff"
                                android:text="Left" />
                        <TextView
                                android:layout_width="0dp"
                                android:layout_height="wrap_content"
                                android:layout_weight="10"
                                android:background="#0f0"
                                android:gravity="center"
                                android:textSize="20dp"
                                android:textColor="#fff"
                                android:text="Right" />
                        <TextView
                                android:id="@+id/tv_view_number"
                                android:layout_width="0dp"
                                android:layout_height="wrap_content"
                                android:layout_weight="10"
                                android:background="#00f"
                                android:gravity="center"
                                android:textSize="20dp"
                                android:textColor="#fff"
                                android:text="No " />
                    </LinearLayout>
                

                    public class InflatorActivity extends AppCompatActivity {
                        Context context;
                        @Override
                        protected void onCreate(Bundle savedInstanceState) {
                            super.onCreate(savedInstanceState);
                            context = this;
                            LinearLayout llMain = new LinearLayout(context);
                            llMain.setOrientation(LinearLayout.VERTICAL);
                            setContentView(llMain);
                            for (int i = 0; i < 10; i++) {
                                //deserialization of view
                                LinearLayout linearLayoutSmallView = (LinearLayout) LayoutInflater.from(context).inflate(R.layout.small_view,null);
                                TextView textViewNumberView = linearLayoutSmallView.findViewById(R.id.tv_view_number);
                                textViewNumberView.setText("No : " + (i+1));
                                llMain.addView(linearLayoutSmallView);
                            }
                        }
                    }
                

                Intent intent = new Intent(ctx,ClassName.class);
                startActivity(intent);
            

                            Intent intent = new Intent(this, SecondeActivity.class);
                            intent.putExtra("name","user name");
                            intent.putExtra("id", "456-fesdf-464sdf");
                            intent.putExtra("year", 27);
                            startActivity(intent);
                        

                            Intent intent = getIntent();
                            String nameValue = intent.getStringExtra("name");
                            String idValue = intent.getStringExtra("id");
                            int yearValue =  intent.getIntExtra("year", -1);
                        

                ActivityResultLauncher<Intent> resultActivity = registerForActivityResult(
                        new ActivityResultContracts.StartActivityForResult(),
                        new ActivityResultCallback<ActivityResult>() {
                            @Override
                            public void onActivityResult(ActivityResult result) {
                                if (result.getResultCode() == RESULT_OK) {
                                    //do instruction when result
                                    Intent intent = result.getData();
                                    String dataString = intent.getStringExtra("dataKey");
                                }
                            }
                        }
                );
                Intent intent = new Intent(this, SecondeActivity.class);
                resultActivity.launch(intent);
            

                button.setOnClickListener(new View.OnClickListener() {
                    @Override
                    public void onClick(View v) {
                        Intent intent = new Intent();
                        intent.putExtra("dataKey","hello data"); //1
                        setResult(RESULT_OK, intent); //2
                        finish(); //3
                    }
                });
            

                    MyProject/
                        src/
                            MyActivity.java
                        res/
                            drawable/
                                graphic.png
                            layout/
                                main.xml
                                info.xml
                            mipmap/
                                icon.png
                            values/
                                strings.xml
                

                    public class R {
                        public static class layout{
                            public static final int activity_main = 0xabc123;
                            public static final int my_layout = 0xabc124;
                            public static final int other_layout = 0xabc125;
                        }
                        public static class drawable{
                            public static final int image1 = 0xbcd123;
                            public static final int image2 = 0xbcd124;
                            public static final int chat = 0xbcd125;
                        }
                        public static class string{
                            public static final int msg_welcom = 0xefa123;
                            public static final int app_name = 0xefa124;
                            public static final int msg_btn_send = 0xefa125;
                        }
                        public static class color{
                            public static final int color_texte = 0x456fa12;
                            public static final int color_btn = 0x456fa13;
                            public static final int color_border = 0x456fa14;
                            public static final int color_title = 0x456fa15;
                        }
                    }
                

                    Resources resources = context.getResources();
                    String stringRessource = resources.getString(R.string.key_ressource);
                    
                    //XXX resValue = resources.getXXX(id);
                

                    @[package:]type_ressource/nom_ressource
                

                    @+[package:]type/nom
                

                    <string name="dyn1">Hello %1$s, you have %2$d years</string>
                

                    Resources res = context.getResources();
                    String chaine = res.getString(R.string.dyn1, "durand", 32);
                

                    AssetManager assetManager = getAssets(); //into activity
                    AssetManager assetManager = context.getAssets(); // everywhere in application
                    try {
                        InputStream inputStream = assetManager.open("fileName");
                    } catch (IOException e) {
                        throw new RuntimeException(e);
                    }
                

                    InputStream inputStream = assetManager.open("fileName");
                    Drawable drawableImage = Drawable.createFromStream(inputStream, null);
                    Bitmap bitmapImage = BitmapFactory.decodeStream(inputStream);
                

                                <menu xmlns:android="http://schemas.android.com/apk/res/android"
                                    xmlns:app="http://schemas.android.com/apk/res-auto">
                                <item
                                        android:id="@+id/menu_play"
                                        android:icon="@android:drawable/ic_media_play"
                                        android:title="play"
                                        app:showAsAction="always" />
                                <item
                                        android:id="@+id/menu_stop"
                                        android:icon="@android:drawable/ic_media_stop"
                                        android:title="stop"
                                        app:showAsAction="always" />
                                <item
                                        android:id="@+id/menu_next"
                                        android:title="next"
                                        app:showAsAction="always" />
                                <item
                                        android:id="@+id/menu_pause"
                                        android:icon="@android:drawable/ic_media_pause"
                                        android:title="pause"
                                        app:showAsAction="ifRoom" />
                                <item
                                        android:id="@+id/menu_reset"
                                        android:title="reset"
                                        app:showAsAction="never" />
                            </menu>
                            

                @Override
                public boolean onCreateOptionsMenu(Menu menu) {
                    MenuInflater menuInflater = getMenuInflater();
                    menuInflater.inflate(R.menu.layout_menu, menu);
                    return true;
                }
            

                @Override
                public boolean onCreateOptionsMenu(Menu menu) {
                    int idItem = 1;        // exemple pour ajouter un item
                    int order = 1;
                    MenuItem menuItem = menu.add(0, idItem, order, "mon menu");
                    return true;
                }
            

                @Override
                public boolean onOptionsItemSelected(@NonNull MenuItem item) {
                    boolean retour = super.onOptionsItemSelected(item);
                    switch (item.getItemId()) {
                        case R.id.menu_play:
                            //action todo
                            retour = true;
                            break;
                        case R.id.menu_stop:
                            //action todo
                            retour = true;
                            break;
                        case R.id.menu_pause:
                            //action todo
                            retour = true;
                            break;
                        case R.id.menu_next:
                            //action todo
                            retour = true;
                            break;
                        case R.id.menu_reset:
                            //action todo
                            retour = true;
                            break;
                    }
                    return retour;
                }
            

                AlertDialog.Builder builder = new AlertDialog.Builder(context);
                builder.setTitle("my wonderful title");
                builder.setMessage("my beautiful Message to print ");
                AlertDialog dialog = builder.create();
                dialog.show();
                //or
                AlertDialog dialog = builder.show();
            

                AlertDialog.Builder builder = new AlertDialog.Builder(context);
                builder.setTitle("my wonderful title");
                builder.setMessage("my beautiful Message to print ");
                builder.setPositiveButton("Yes", new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialog, int which) {
                        //action if yes is select
                    }
                });
                builder.setNeutralButton("i don't know", new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialog, int which) {
                        //action if i don't know is select
                    }
                });
                builder.setPositiveButton("no", new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialog, int which) {
                        //action if no select
                    }
                });
                AlertDialog dialog = builder.show();
            

                String[] items = new String[]{"orange","blue","green"};
                AlertDialog.Builder builder = new AlertDialog.Builder(context);
                builder.setTitle("my wonderful title");
                builder.setItems(items, new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialog, int which) {
                        String value = items[which];//which = position of item select
                    }
                });
                AlertDialog dialog = builder.show();
            

                <string-array name="colors_list">
                    <item>orange</item>
                    <item>blue</item>
                    <item>green</item>
                </string-array>
            

                builder.setItems(R.array.colors_list, new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialog, int which) {
                        String[] items = getResources().getStringArray(R.array.colors_list); //pour récupérer les données depuis le répertoire Ressource
                        String value = items[which];//which = position of item select
                    }
                });
            

vue définie en xml

                <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
                        android:layout_width="match_parent"
                        android:layout_height="match_parent"
                        android:orientation="vertical">
                    <LinearLayout
                            android:layout_width="match_parent"
                            android:layout_height="wrap_content"
                            android:orientation="horizontal">
                        <TextView
                                android:layout_width="0px"
                                android:layout_height="wrap_content"
                                android:layout_weight="30"
                                android:text="login : " />
                        <EditText
                                android:id="@+id/ed_login_ad"
                                android:layout_width="0px"
                                android:layout_height="wrap_content"
                                android:layout_weight="70" />
                    </LinearLayout>
                    <LinearLayout
                            android:layout_width="match_parent"
                            android:layout_height="wrap_content"
                            android:orientation="horizontal">
                        <TextView
                                android:layout_width="0px"
                                android:layout_height="wrap_content"
                                android:layout_weight="30"
                                android:text="password : " />
                        <EditText
                                android:id="@+id/ed_password_ad"
                                android:layout_width="0px"
                                android:layout_height="wrap_content"
                                android:layout_weight="70" />
                    </LinearLayout>
                </LinearLayout>
            

code java pour un alert dialog avec une vue perso

                AlertDialog.Builder builder = new AlertDialog.Builder(context);
                builder.setTitle("my wonderful title");
                View view = LayoutInflater.from(context).inflate(R.layout.alert_dialog_layout,null);
                builder.setView(view);
                AlertDialog dialog = builder.show();
                

                EditText edLogin = view.findViewById(R.id.ed_login_ad);
            

                builder.setPositiveButton("Yes", new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialog, int which) {
                        AlertDialog alertDialog = (AlertDialog) dialog;
                        EditText edLogin = alertDialog.findViewById(R.id.ed_login_ad);
                    }
                });
            

                    view.setOnClickListener(new View.OnClickListener() {
                        @Override
                        public void onClick(View v) {
                            //action to do
                            v.setBackgroundColor(Color.GREEN);
                        }
                    });
                

                    view.setOnLongClickListener(new View.OnLongClickListener() {
                        @Override
                        public boolean onLongClick(View v) {
                            return true;
                        }
                    });
                

                    view.setOnFocusChangeListener(new View.OnFocusChangeListener() {
                        @Override
                        public void onFocusChange(View v, boolean hasFocus) {
                            if(hasFocus){
                                v.setBackgroundColor(Color.GREEN);
                            }else{
                                v.setBackgroundColor(Color.BLUE);
                            }
                        }
                    });
                

                    editText.addTextChangedListener(new TextWatcher() {
                        @Override
                        public void beforeTextChanged(CharSequence s, int start, int count, int after) {
                        }
                        @Override
                        public void onTextChanged(CharSequence s, int start, int before, int count) {
                        }
                        @Override
                        public void afterTextChanged(Editable s) {
                        }
                    });
                

                    radioButton.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {
                        @Override
                        public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
                        }
                    });
                

                    public class MainActivity extends AppCompactActivity {
                    ...
                    // exemple pour une activité, mais même approche pour une sous classe de View
                    @Override
                    public boolean onTouchEvent(MotionEvent event){
                    
                        int action = MotionEventCompat.getActionMasked(event);
                    
                        switch(action) {
                            case (MotionEvent.ACTION_DOWN) :
                                Log.d(DEBUG_TAG,"Action was DOWN");
                                return true;
                            case (MotionEvent.ACTION_MOVE) :
                                Log.d(DEBUG_TAG,"Action was MOVE");
                                return true;
                            case (MotionEvent.ACTION_UP) :
                                Log.d(DEBUG_TAG,"Action was UP");
                                return true;
                            case (MotionEvent.ACTION_OUTSIDE) :
                                Log.d(DEBUG_TAG,"Movement occurred outside bounds " +
                                        "of current screen element");
                                return true;
                            default :
                                return super.onTouchEvent(event);
                        }
                    }
                    
                    //exemple sur une sous-classe de View
                    View myView = findViewById(R.id.my_view);
                    myView.setOnTouchListener(new OnTouchListener() {
                        public boolean onTouch(View v, MotionEvent event) {
                            //action to do
                            return true;
                        }
                    });
                    
                

                    @Override
                    public boolean onTouchEvent(MotionEvent event) {
                        float xPosition = 0;
                        float yPosition = 0;
                        if(event.getActionMasked() == MotionEvent.ACTION_DOWN){
                            xPosition = event.getX();
                            yPosition = event.getY();
                        }
                        if(event.getActionMasked() == MotionEvent.ACTION_MOVE){
                            xPosition = event.getX();
                            yPosition = event.getY();
                        }
                        return super.onTouchEvent(event);
                    }
                

                    @Override
                    public boolean onTouchEvent(MotionEvent event) {
                        // get pointer index from the event object
                        int pointerIndex = event.getActionIndex();
                        // get pointer ID from pointerIndex
                        int pointerId = event.getPointerId(pointerIndex);
                        // get action
                        int maskedAction = event.getActionMasked();
                        switch (maskedAction) {
                            case MotionEvent.ACTION_DOWN:
                                Log.d(TAG, "index down: " + pointerId);
                                break;
                            case MotionEvent.ACTION_POINTER_DOWN: {
                                Log.d(TAG, "index down: " + pointerId);
                                break;
                            }
                            case MotionEvent.ACTION_MOVE: { // a pointer was moved
                                Log.d(TAG, "index move: " + pointerId);
                                break;
                            }
                            case MotionEvent.ACTION_UP:
                                Log.d(TAG, "index up: " + pointerId);
                
                                break;
                            case MotionEvent.ACTION_POINTER_UP:
                                Log.d(TAG, "index up: " + pointerId);
                                break;
                        }
                
                        return true;
                    }
                

                            public class EventActivity extends AppCompatActivity implements GestureDetector.OnGestureListener {
                                Context context;
                                @Override
                                protected void onCreate(Bundle savedInstanceState) {
                                    super.onCreate(savedInstanceState);
                                    context = this;
                                    setContentView(R.layout.activity_event);
                                }
                                @Override
                                public boolean onDown(MotionEvent e) {
                                    return false;
                                }
                                @Override
                                public void onShowPress(MotionEvent e) {
                                }
                                @Override
                                public boolean onSingleTapUp(MotionEvent e) {
                                    return false;
                                }
                                @Override
                                public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY) {
                                    return false;
                                }
                                @Override
                                public void onLongPress(MotionEvent e) {
                                }
                                @Override
                                public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY) {
                                    return false;
                                }
                            }
                        

                    public class EventActivity extends AppCompatActivity implements GestureDetector.OnGestureListener {
                        private String TAG = "debug-app";
                        GestureDetector gestureDetector;
                        Context context;
                        @Override
                        protected void onCreate(Bundle savedInstanceState) {
                            super.onCreate(savedInstanceState);
                            context = this;
                            setContentView(R.layout.activity_event);
                            gestureDetector = new GestureDetector(this,this);
                        }
                        @Override
                        public boolean onDown(MotionEvent e) {
                            return false;
                        }
                        @Override
                        public void onShowPress(MotionEvent e) {
                        }
                        @Override
                        public boolean onSingleTapUp(MotionEvent e) {
                            return false;
                        }
                        @Override
                        public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY) {
                            return false;
                        }
                        @Override
                        public void onLongPress(MotionEvent e) {
                        }
                        @Override
                        public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY) {
                            return false;
                        }
                    }
                

                    public class EventActivity extends AppCompatActivity implements GestureDetector.OnGestureListener {
                        private String TAG = "debug-app";
                        GestureDetector gestureDetector;
                        Context context;
                        @Override
                        protected void onCreate(Bundle savedInstanceState) {
                            super.onCreate(savedInstanceState);
                            context = this;
                            setContentView(R.layout.activity_event);
                            gestureDetector = new GestureDetector(this,this);
                        }
                        @Override
                        public boolean onTouchEvent(MotionEvent event) {
                            gestureDetector.onTouchEvent(event);
                            return true;
                        }
                        @Override
                        public boolean onDown(MotionEvent e) {
                            return false;
                        }
                        @Override
                        public void onShowPress(MotionEvent e) {
                        }
                        @Override
                        public boolean onSingleTapUp(MotionEvent e) {
                            return false;
                        }
                        @Override
                        public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY) {
                            return false;
                        }
                        @Override
                        public void onLongPress(MotionEvent e) {
                        }
                        @Override
                        public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY) {
                            return false;
                        }
                    }
                

                //si pas besoin de catégoriser les informations
                SharedPreferences sharedPreferences = PreferenceManager.getDefaultSharedPreferences(this);
                //si besoin de catégoriser
                SharedPreferences sharedPreferencesUser = context.getSharedPreferences("user", Context.MODE_PRIVATE);
            

                SharedPreferences sharedPreferences = PreferenceManager.getDefaultSharedPreferences(this);
                String guid = sharedPreferences.getString("id",null);
                int age = sharedPreferences.getInt("age",-1);
            

                SharedPreferences sharedPreferences = PreferenceManager.getDefaultSharedPreferences(this);
                SharedPreferences.Editor editor = sharedPreferences.edit();
                editor.putString("userName", "John Doe");
                editor.putFloat("xPosition", 42.56f);
                editor.putFloat("yPosition", 1056.89f);
                editor.apply();
            

                SharedPreferences sharedPreferences = PreferenceManager.getDefaultSharedPreferences(this);
                SharedPreferences.Editor editor = sharedPreferences.edit();
               
                //suppression par clef
                editor.remove("userName");
                editor.remove("id");
                editor.apply();
               
                //suppression total
                editor.clear();
                editor.apply();
            

            File file = new File(context.getFilesDir(), filename);
            

                String filename = "myFile.txt";
                String fileContents = "Hello world!";
                try (FileOutputStream fos = context.openFileOutput(filename, Context.MODE_PRIVATE)) {
                    fos.write(fileContents.toByteArray());
                }
            

                FileInputStream fileInputStream = context.openFileInput(fileName);
                InputStreamReader inputStreamReader =
                        new InputStreamReader(fileInputStream, StandardCharsets.UTF_8);
                StringBuilder stringBuilder = new StringBuilder();
                try (BufferedReader reader = new BufferedReader(inputStreamReader)) {
                    String line = reader.readLine();
                    while (line != null) {
                        stringBuilder.append(line).append('\n');
                        line = reader.readLine();
                    }
                } catch (IOException e) {
                    // Error occurred when opening raw file for reading.
                } finally {
                    String contents = stringBuilder.toString();
                }
            

                <uses-permission android:name="android.permission.MANAGE_EXTERNAL_STORAGE" />
            

                    File file = new File(Environment.getExternalStorageDirectory().getPath()+ File.separator+ "Android/data"+File.separator + getPackageName() + "/files/"+"myFile.txt" );
                

                CREATE TABLE etudiant (
                    id INTEGER PRIMARY KEY AUTOINCREMENT,
                    first_name TEXT,
                    last_name TEXT,
                    age
                );
            

                public class DataBaseHelper extends SQLiteOpenHelper {
                    public DataBaseHelper(@Nullable Context context, @Nullable String name, @Nullable SQLiteDatabase.CursorFactory factory, int version) {
                        super(context, name, factory, version);
                    }
                    @Override
                    public void onCreate(SQLiteDatabase db) {
                    }
                    @Override
                    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
                    }
                }
            

                @Override
                public void onCreate(SQLiteDatabase db) {
                    db.execSQL("CREATE TABLE etudiant (\n" +
                            "id INTEGER PRIMARY KEY AUTOINCREMENT," +
                            "first_name TEXT," +
                            "last_name TEXT," +
                            "age" +
                            ");");
                    db.execSQL("INSERT INTO etudiant ('first_name','last_name','age') values ('john','doe', 27), ('foo','bar',99);");
                }
                @Override
                public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
                    db.execSQL("DROP TABLE IF EXISTS etudiant");
                    onCreate(db);
                }
            

                public class ConnectionDB {
                    private static int version = 1;
                    private static String bnName = "myBd.db";
                    private static SQLiteDatabase bd = null;
                    private static DataBaseHelper helper;
                    
                    public static SQLiteDatabase getBd(Context context){
                        if(helper == null){
                            helper = new DataBaseHelper(context, bnName, null, version);
                        }
                        bd = helper.getWritableDatabase();
                        return bd;
                    }
                    public static void close(){
                        if(bd!= null &&  !bd.isOpen()){
                            bd.close();
                        }
                    }
                }
            

                    public class EtudiantManager {
                    
                        public static long add(Context context, Etudiant etudiantToAdd){
                            ContentValues contentValues = new ContentValues();
                            contentValues.put("first_name", etudiantToAdd.getFirstName());
                            contentValues.put("last_name", etudiantToAdd.getLastName());
                            contentValues.put("age", etudiantToAdd.getAge());
                            SQLiteDatabase bd = ConnectionDB.getBd(context); //on réutilise ConnctionDB ici
                            return bd.insert("etudiant", null, contentValues);
                        }
                    }
                

                public static void delete(Context context, int idEtudiant){
                    SQLiteDatabase bd = ConnectionDB.getBd(context);
                    bd.delete("etudiant","id = ?" , new String[]{String.valueOf(idEtudiant)});
                }
            

                public int delete (String table,
                                    String whereClause,
                                    String[] whereArgs)
            

                DELETE FROM etudiant WHERE id = ?
            

                DELETE FROM etudiant WHERE id = 7
            

                    DELETE FROM etudiant WHERE id = ? AND name LIKE ?
                

                    public static void update(Context context, Etudiant etudiantToUpdate) {
                        ContentValues contentValues = new ContentValues();
                        contentValues.put("first_name", etudiantToUpdate.getFirstName());
                        contentValues.put("age", etudiantToUpdate.getAge());
                        SQLiteDatabase bd = ConnectionDB.getBd(context);
                        long nbRowChange = bd.update("etudiant", contentValues, "id = ?", new String[]{String.valueOf(etudiantToUpdate.getId())});
                    }
                

                    public static ArrayList<Etudiant> getAll(Context context) {
                        SQLiteDatabase bd = ConnectionDB.getBd(context);
                        String query = "SELECT * FROM etudiant";
                        ArrayList<Etudiant> etudiants = null;
                        Cursor cursor = bd.rawQuery(query, null);
                        if (cursor.isBeforeFirst()) {
                            etudiants = new ArrayList<>();
                            while (cursor.moveToNext()) {
                                Etudiant etudiant = new Etudiant();
                                etudiant.setId(cursor.getInt(cursor.getColumnIndexOrThrow("id")));
                                etudiant.setFirstName(cursor.getString(cursor.getColumnIndexOrThrow("first_name")));
                                etudiant.setLastName(cursor.getString(cursor.getColumnIndexOrThrow("last_name")));
                                etudiant.setAge(cursor.getInt(cursor.getColumnIndexOrThrow("age")));
                                etudiants.add(etudiant);
                            }
                        }
                        return etudiants;
                    }
                

                public static ArrayList<Etudiant> getByAgeLimite(Context context, int ageLimite) {
                    SQLiteDatabase bd = ConnectionDB.getBd(context);
                    String query = "SELECT * FROM etudiant where age > ?";
                    ArrayList<Etudiant> etudiants = null;
                    Cursor cursor = bd.rawQuery(query, new String[]{String.valueOf(ageLimite)});
                    if (cursor.isBeforeFirst()) {
                        etudiants = new ArrayList<>();
                        while (cursor.moveToNext()) {
                            Etudiant etudiant = new Etudiant();
                            etudiant.setId(cursor.getInt(cursor.getColumnIndexOrThrow("id")));
                            etudiant.setFirstName(cursor.getString(cursor.getColumnIndexOrThrow("first_name")));
                            etudiant.setLastName(cursor.getString(cursor.getColumnIndexOrThrow("last_name")));
                            etudiant.setAge(cursor.getInt(cursor.getColumnIndexOrThrow("age")));
                            etudiants.add(etudiant);
                        }
                    }
                    return etudiants;
                }
                

                    SensorManager sensorManager = (SensorManager) getSystemService(Context.SENSOR_SERVICE);
                

                    List<Sensor> sensors = sensorManager.getSensorList(Sensor.TYPE_ALL);
                    for (Sensor sensor : sensors) {
                        Log.d("debug_app", "sensor: " + sensor.getName());
                        Log.d("debug_app", "sensor: " + sensor.getMinDelay());
                        Log.d("debug_app", "sensor: " + sensor.getVersion());
                        Log.d("debug_app", "sensor: " + sensor.getMaximumRange());
                    }
                

                    Sensor sensorLight = sensorManager.getDefaultSensor(Sensor.TYPE_LIGHT);
                    if(sensorLight != null){
                        // sensor existe
                    } else {
                        // prévenir l'utilisateur qu'on ne peut pas continuer
                    }
                

                SensorEventListener sensorEventListener = new SensorEventListener() {
                    @Override
                    public void onSensorChanged(SensorEvent event) {
                    }
                    @Override
                    public void onAccuracyChanged(Sensor sensor, int accuracy) {
                    }
                };
                

                    @Override
                    protected void onResume() {
                        super.onResume();
                        sensorManager.registerListener(sensorEventListener, sensorLight, SensorManager.SENSOR_DELAY_FASTEST);
                    }
                

                    @Override
                    protected void onPause() {
                        super.onPause();
                        sensorManager.unregisterListener(sensorEventListener,sensorLight);
                    }
                

                    public class SensorActivity extends AppCompatActivity {
                        TextView textView;
                        SensorManager sensorManager;
                        SensorEventListener sensorEventListener;
                        Sensor sensorLight;
                        @Override
                        protected void onCreate(Bundle savedInstanceState) {
                            super.onCreate(savedInstanceState);
                            setContentView(R.layout.activity_sensor);
                            textView = findViewById(R.id.text);
                            sensorManager = (SensorManager) getSystemService(Context.SENSOR_SERVICE);
                            sensorLight = sensorManager.getDefaultSensor(Sensor.TYPE_LIGHT);
                            sensorEventListener = new SensorEventListener() {
                                @Override
                                public void onSensorChanged(SensorEvent event) {
                                    float luxValue = event.values[0];
                                    textView.setText(String.valueOf(luxValue) + " lux");
                                }
                                @Override
                                public void onAccuracyChanged(Sensor sensor, int accuracy) {
                                }
                            };
                        }
                        @Override
                        protected void onResume() {
                            super.onResume();
                            sensorManager.registerListener(sensorEventListener, sensorLight, SensorManager.SENSOR_DELAY_FASTEST);
                        }
                        @Override
                        protected void onPause() {
                            super.onPause();
                            sensorManager.unregisterListener(sensorEventListener,sensorLight);
                        }
                    }
                

                    <uses-feature android:name="android.hardware.sensor.accelerometer"
                                  android:required="true" />
                

                    <?xml version="1.0" encoding="utf-8"?>
                    <manifest
                        xmlns:android="http://schemas.android.com/apk/res/android"
                        android:versionCode="1"
                        android:versionName="1.0">
                    
                        <uses-feature android:name="android.hardware.sensor.compass"
                            android:required="true" />
                    
                        <application
                            android:allowBackup="true"
                            android:icon="@mipmap/ic_launcher"
                            android:roundIcon="@mipmap/ic_launcher_round"
                            android:label="@string/app_name"
                            android:supportsRtl="true"
                            android:theme="@style/AppTheme">
                    
                            <activity android:name=".MainActivity">
                                <intent-filter>
                                    <action android:name="android.intent.action.MAIN" />
                                    <category android:name="android.intent.category.LAUNCHER" />
                                </intent-filter>
                            </activity>
                            <activity
                                android:name=".DisplayMessageActivity"
                                android:parentActivityName=".MainActivity" />
                        </application>
                    </manifest>
            

                plugins {
                    id 'com.android.application'
                }
                android {
                    namespace 'com.example.appname'
                    compileSdk 32
                    defaultConfig {
                        applicationId "com.example.appname"
                        minSdk 25
                        targetSdk 32
                        versionCode 1
                        versionName "1.0"
                        testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
                    }
                    buildTypes {
                        release {
                            minifyEnabled false
                            proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
                        }
                    }
                    compileOptions {
                        sourceCompatibility JavaVersion.VERSION_1_8
                        targetCompatibility JavaVersion.VERSION_1_8
                    }
                }
                dependencies {
                    implementation 'androidx.appcompat:appcompat:1.5.1'
                    implementation 'com.google.android.material:material:1.7.0'
                    implementation 'androidx.constraintlayout:constraintlayout:2.1.4'
                    testImplementation 'junit:junit:4.13.2'
                    androidTestImplementation 'androidx.test.ext:junit:1.1.3'
                    androidTestImplementation 'androidx.test.espresso:espresso-core:3.4.0'
                }
            

                    public class MainActivity extends AppCompatActivity {
                        @Override
                        protected void onCreate(Bundle savedInstanceState) {
                            super.onCreate(savedInstanceState);
                            setContentView(R.layout.activity_main);
                        }
                    }
                

                public class MainActivity extends AppCompatActivity {
                    private static final String TAG = "debug_app";
                    @Override
                    protected void onCreate(Bundle savedInstanceState) {
                        super.onCreate(savedInstanceState);
                        setContentView(R.layout.activity_main);
                        Log.d(TAG, "onCreate:");
                    }
                    @Override
                    protected void onStart() {
                        super.onStart();
                        Log.d(TAG, "onStart: ");
                    }
                    @Override
                    protected void onResume() {
                        super.onResume();
                        Log.d(TAG, "onResume: ");
                    }
                    @Override
                    protected void onPause() {
                        super.onPause();
                        Log.d(TAG, "onPause: ");
                    }
                    @Override
                    protected void onStop() {
                        super.onStop();
                        Log.d(TAG, "onStop: ");
                    }
                    @Override
                    protected void onDestroy() {
                        super.onDestroy();
                        Log.d(TAG, "onDestroy: ");
                    }
                }
            

                public class FirstActivity extends Activity {
                }
            

                public class FirstActivity extends AppCompatActivity {
                    @Override
                    protected void onCreate(@Nullable Bundle savedInstanceState) {
                        super.onCreate(savedInstanceState);
                        setContentView(R.layout.activity_first);
                    }
                }
            

                <application
                       ... >
                    <activity android:name=".FirstActivity"
                        android:exported="true">
                        <intent-filter>
                            <action android:name="android.intent.action.MAIN" />
                            <category android:name="android.intent.category.LAUNCHER" />
                        </intent-filter>
                    </activity>
                </application>
            

                <application
                       ... >
                    <activity android:name=".FirstActivity"
                        android:exported="true">
                        <intent-filter>
                            <action android:name="android.intent.action.MAIN" />
                            <category android:name="android.intent.category.LAUNCHER" />
                        </intent-filter>
                    </activity>
                    <activity android:name=".SecondActivité"
                        android:exported="false"/>
                </application>
            

                public class MainActivity extends AppCompatActivity {
                    Context context;
                    @Override
                    protected void onCreate(Bundle savedInstanceState) {
                        super.onCreate(savedInstanceState);
                        context = this; //don t forget this line, else you will have NullPointer
                        setContentView(R.layout.activity_main);
                    }
                }
            

                    android:id="@+id/my_id"
                

                    <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
                            xmlns:app="http://schemas.android.com/apk/res-auto"
                            xmlns:tools="http://schemas.android.com/tools"
                            android:layout_width="match_parent"
                            android:layout_height="match_parent"
                            android:orientation="vertical"
                            tools:context=".MainActivity">
                        <TextView
                                android:layout_width="match_parent"
                                android:layout_height="wrap_content"
                                android:text="Hello World!" />
                        <TextView
                                android:layout_width="wrap_content"
                                android:layout_height="wrap_content"
                                android:layout_gravity="right"
                                android:text="Hello World!" />
                        <TextView
                                android:layout_width="match_parent"
                                android:gravity="right"
                                android:layout_height="wrap_content"
                                android:text="Hello World!" />
                        <TextView
                                android:layout_width="wrap_content"
                                android:layout_height="wrap_content"
                                android:layout_gravity="center"
                                android:text="Hello World!" />
                    </LinearLayout>
                

                    <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
                            xmlns:app="http://schemas.android.com/apk/res-auto"
                            xmlns:tools="http://schemas.android.com/tools"
                            android:layout_width="match_parent"
                            android:layout_height="match_parent"
                            android:orientation="vertical"
                            tools:context=".MainActivity">
                        <Button
                                android:layout_width="match_parent"
                                android:layout_height="0dp"
                                android:layout_weight="40"
                                android:text="btn 1" />
                        <Button
                                android:layout_width="match_parent"
                                android:layout_height="0dp"
                                android:layout_weight="60"
                                android:text="btn 2" />
                    </LinearLayout>
                

                    <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
                            xmlns:app="http://schemas.android.com/apk/res-auto"
                            xmlns:tools="http://schemas.android.com/tools"
                            android:layout_width="match_parent"
                            android:layout_height="match_parent"
                            android:orientation="horizontal"
                            tools:context=".MainActivity">
                        <Button
                                android:layout_width="0dp"
                                android:layout_height="match_parent"
                                android:layout_weight="2"
                                android:text="btn 1" />
                        <Button
                                android:layout_width="0dp"
                                android:layout_height="match_parent"
                                android:layout_weight="5"
                                android:text="btn 2" />
                    </LinearLayout>
                

                    public class MainActivity extends AppCompatActivity {
                        Context context;
                        @Override
                        protected void onCreate(Bundle savedInstanceState) {
                            super.onCreate(savedInstanceState);
                            context = this;
                            //set UI width XML File
                            setContentView(R.layout.activity_main); //we give here reference of XML file
                            
                            //set view width Java File
                            LinearLayout container = new LinearLayout(context);
                            setContentView(container);
                        }
                    }
                

                        <?xml version="1.0" encoding="utf-8"?>
                        <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
                                xmlns:app="http://schemas.android.com/apk/res-auto"
                                xmlns:tools="http://schemas.android.com/tools"
                                android:layout_width="match_parent"
                                android:layout_height="match_parent"
                                android:orientation="vertical"
                                tools:context=".MainActivity">
                            <TextView
                                    android:layout_width="wrap_content"
                                    android:layout_height="wrap_content"
                                    android:text="Hello World!" />
                        </LinearLayout>
                

                    public class MainActivity extends AppCompatActivity {
                        @Override
                        protected void onCreate(Bundle savedInstanceState) {
                            super.onCreate(savedInstanceState);
                            setContentView(R.layout.activity_main);
                        }
                    }
                

                TextView tv = new TextView(this);
                LinearLayout.LayoutParams params = new LinearLayout.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.WRAP_CONTENT);
                tv.setLayoutParams(params);
                

                    public class MainActivity extends AppCompatActivity {
                        Context context;
                        @Override
                        protected void onCreate(Bundle savedInstanceState) {
                            super.onCreate(savedInstanceState);
                            context = this;
                            //create instance of linear layout
                            LinearLayout linearLayoutMain = new LinearLayout(context);
                            linearLayoutMain.setLayoutParams(new LinearLayout.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.MATCH_PARENT));
                            linearLayoutMain.setOrientation(LinearLayout.VERTICAL);
                            //add linearLayout as main container of activity
                            setContentView(linearLayoutMain);
                            //create textview
                            TextView textView = new TextView(context);
                            textView.setText("Hello World!");
                            textView.setLayoutParams(new LinearLayout.LayoutParams(ViewGroup.LayoutParams.WRAP_CONTENT, ViewGroup.LayoutParams.WRAP_CONTENT));
                            //set text view as child of linearlayout
                            linearLayoutMain.addView(textView);
                        }
                    }
                

                    <?xml version="1.0" encoding="utf-8"?>
                    <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
                            xmlns:app="http://schemas.android.com/apk/res-auto"
                            xmlns:tools="http://schemas.android.com/tools"
                            android:layout_width="match_parent"
                            android:layout_height="match_parent"
                            android:orientation="vertical"
                            tools:context=".MainActivity">
                        <TextView
                                android:id="@+id/text_view"
                                android:layout_width="wrap_content"
                                android:layout_height="wrap_content"
                                android:text="Hello World!" />
                    </LinearLayout>
                

                    public class MainActivity extends AppCompatActivity {
                        Context context;
                        @Override
                        protected void onCreate(Bundle savedInstanceState) {
                            super.onCreate(savedInstanceState);
                            context = this;
                            setContentView(R.layout.activity_main);
                            //access to textview
                            TextView textView = findViewById(R.id.text_view);
                            //change value of textview
                            textView.setText("New text to print");
                        }
                    }
                

                    <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
                            android:layout_width="match_parent"
                            android:layout_height="match_parent"
                            android:orientation="horizontal"
                            android:padding="5dp">
                        <TextView
                                android:layout_width="0dp"
                                android:layout_height="wrap_content"
                                android:layout_weight="10"
                                android:background="#f00"
                                android:gravity="center"
                                android:textSize="20dp"
                                android:textColor="#fff"
                                android:text="Left" />
                        <TextView
                                android:layout_width="0dp"
                                android:layout_height="wrap_content"
                                android:layout_weight="10"
                                android:background="#0f0"
                                android:gravity="center"
                                android:textSize="20dp"
                                android:textColor="#fff"
                                android:text="Right" />
                        <TextView
                                android:id="@+id/tv_view_number"
                                android:layout_width="0dp"
                                android:layout_height="wrap_content"
                                android:layout_weight="10"
                                android:background="#00f"
                                android:gravity="center"
                                android:textSize="20dp"
                                android:textColor="#fff"
                                android:text="No " />
                    </LinearLayout>
                

                    public class InflatorActivity extends AppCompatActivity {
                        Context context;
                        @Override
                        protected void onCreate(Bundle savedInstanceState) {
                            super.onCreate(savedInstanceState);
                            context = this;
                            LinearLayout llMain = new LinearLayout(context);
                            llMain.setOrientation(LinearLayout.VERTICAL);
                            setContentView(llMain);
                            for (int i = 0; i < 10; i++) {
                                //deserialization of view
                                LinearLayout linearLayoutSmallView = (LinearLayout) LayoutInflater.from(context).inflate(R.layout.small_view,null);
                                TextView textViewNumberView = linearLayoutSmallView.findViewById(R.id.tv_view_number);
                                textViewNumberView.setText("No : " + (i+1));
                                llMain.addView(linearLayoutSmallView);
                            }
                        }
                    }
                

                Intent intent = new Intent(ctx,ClassName.class);
                startActivity(intent);
            

                            Intent intent = new Intent(this, SecondeActivity.class);
                            intent.putExtra("name","user name");
                            intent.putExtra("id", "456-fesdf-464sdf");
                            intent.putExtra("year", 27);
                            startActivity(intent);
                        

                            Intent intent = getIntent();
                            String nameValue = intent.getStringExtra("name");
                            String idValue = intent.getStringExtra("id");
                            int yearValue =  intent.getIntExtra("year", -1);
                        

                ActivityResultLauncher<Intent> resultActivity = registerForActivityResult(
                        new ActivityResultContracts.StartActivityForResult(),
                        new ActivityResultCallback<ActivityResult>() {
                            @Override
                            public void onActivityResult(ActivityResult result) {
                                if (result.getResultCode() == RESULT_OK) {
                                    //do instruction when result
                                    Intent intent = result.getData();
                                    String dataString = intent.getStringExtra("dataKey");
                                }
                            }
                        }
                );
                Intent intent = new Intent(this, SecondeActivity.class);
                resultActivity.launch(intent);
            

                button.setOnClickListener(new View.OnClickListener() {
                    @Override
                    public void onClick(View v) {
                        Intent intent = new Intent();
                        intent.putExtra("dataKey","hello data"); //1
                        setResult(RESULT_OK, intent); //2
                        finish(); //3
                    }
                });
            

                    MyProject/
                        src/
                            MyActivity.java
                        res/
                            drawable/
                                graphic.png
                            layout/
                                main.xml
                                info.xml
                            mipmap/
                                icon.png
                            values/
                                strings.xml
                

                    public class R {
                        public static class layout{
                            public static final int activity_main = 0xabc123;
                            public static final int my_layout = 0xabc124;
                            public static final int other_layout = 0xabc125;
                        }
                        public static class drawable{
                            public static final int image1 = 0xbcd123;
                            public static final int image2 = 0xbcd124;
                            public static final int chat = 0xbcd125;
                        }
                        public static class string{
                            public static final int msg_welcom = 0xefa123;
                            public static final int app_name = 0xefa124;
                            public static final int msg_btn_send = 0xefa125;
                        }
                        public static class color{
                            public static final int color_texte = 0x456fa12;
                            public static final int color_btn = 0x456fa13;
                            public static final int color_border = 0x456fa14;
                            public static final int color_title = 0x456fa15;
                        }
                    }
                

                    Resources resources = context.getResources();
                    String stringRessource = resources.getString(R.string.key_ressource);
                    
                    //XXX resValue = resources.getXXX(id);
                

                    @[package:]type_ressource/nom_ressource
                

                    @+[package:]type/nom
                

                    <string name="dyn1">Hello %1$s, you have %2$d years</string>
                

                    Resources res = context.getResources();
                    String chaine = res.getString(R.string.dyn1, "durand", 32);
                

                    AssetManager assetManager = getAssets(); //into activity
                    AssetManager assetManager = context.getAssets(); // everywhere in application
                    try {
                        InputStream inputStream = assetManager.open("fileName");
                    } catch (IOException e) {
                        throw new RuntimeException(e);
                    }
                

                    InputStream inputStream = assetManager.open("fileName");
                    Drawable drawableImage = Drawable.createFromStream(inputStream, null);
                    Bitmap bitmapImage = BitmapFactory.decodeStream(inputStream);
                

                                <menu xmlns:android="http://schemas.android.com/apk/res/android"
                                    xmlns:app="http://schemas.android.com/apk/res-auto">
                                <item
                                        android:id="@+id/menu_play"
                                        android:icon="@android:drawable/ic_media_play"
                                        android:title="play"
                                        app:showAsAction="always" />
                                <item
                                        android:id="@+id/menu_stop"
                                        android:icon="@android:drawable/ic_media_stop"
                                        android:title="stop"
                                        app:showAsAction="always" />
                                <item
                                        android:id="@+id/menu_next"
                                        android:title="next"
                                        app:showAsAction="always" />
                                <item
                                        android:id="@+id/menu_pause"
                                        android:icon="@android:drawable/ic_media_pause"
                                        android:title="pause"
                                        app:showAsAction="ifRoom" />
                                <item
                                        android:id="@+id/menu_reset"
                                        android:title="reset"
                                        app:showAsAction="never" />
                            </menu>
                            

                @Override
                public boolean onCreateOptionsMenu(Menu menu) {
                    MenuInflater menuInflater = getMenuInflater();
                    menuInflater.inflate(R.menu.layout_menu, menu);
                    return true;
                }
            

                @Override
                public boolean onCreateOptionsMenu(Menu menu) {
                    int idItem = 1;        // exemple pour ajouter un item
                    int order = 1;
                    MenuItem menuItem = menu.add(0, idItem, order, "mon menu");
                    return true;
                }
            

                @Override
                public boolean onOptionsItemSelected(@NonNull MenuItem item) {
                    boolean retour = super.onOptionsItemSelected(item);
                    switch (item.getItemId()) {
                        case R.id.menu_play:
                            //action todo
                            retour = true;
                            break;
                        case R.id.menu_stop:
                            //action todo
                            retour = true;
                            break;
                        case R.id.menu_pause:
                            //action todo
                            retour = true;
                            break;
                        case R.id.menu_next:
                            //action todo
                            retour = true;
                            break;
                        case R.id.menu_reset:
                            //action todo
                            retour = true;
                            break;
                    }
                    return retour;
                }
            

                AlertDialog.Builder builder = new AlertDialog.Builder(context);
                builder.setTitle("my wonderful title");
                builder.setMessage("my beautiful Message to print ");
                AlertDialog dialog = builder.create();
                dialog.show();
                //or
                AlertDialog dialog = builder.show();
            

                AlertDialog.Builder builder = new AlertDialog.Builder(context);
                builder.setTitle("my wonderful title");
                builder.setMessage("my beautiful Message to print ");
                builder.setPositiveButton("Yes", new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialog, int which) {
                        //action if yes is select
                    }
                });
                builder.setNeutralButton("i don't know", new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialog, int which) {
                        //action if i don't know is select
                    }
                });
                builder.setPositiveButton("no", new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialog, int which) {
                        //action if no select
                    }
                });
                AlertDialog dialog = builder.show();
            

                String[] items = new String[]{"orange","blue","green"};
                AlertDialog.Builder builder = new AlertDialog.Builder(context);
                builder.setTitle("my wonderful title");
                builder.setItems(items, new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialog, int which) {
                        String value = items[which];//which = position of item select
                    }
                });
                AlertDialog dialog = builder.show();
            

                <string-array name="colors_list">
                    <item>orange</item>
                    <item>blue</item>
                    <item>green</item>
                </string-array>
            

                builder.setItems(R.array.colors_list, new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialog, int which) {
                        String[] items = getResources().getStringArray(R.array.colors_list); //pour récupérer les données depuis le répertoire Ressource
                        String value = items[which];//which = position of item select
                    }
                });
            

vue définie en xml

                <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
                        android:layout_width="match_parent"
                        android:layout_height="match_parent"
                        android:orientation="vertical">
                    <LinearLayout
                            android:layout_width="match_parent"
                            android:layout_height="wrap_content"
                            android:orientation="horizontal">
                        <TextView
                                android:layout_width="0px"
                                android:layout_height="wrap_content"
                                android:layout_weight="30"
                                android:text="login : " />
                        <EditText
                                android:id="@+id/ed_login_ad"
                                android:layout_width="0px"
                                android:layout_height="wrap_content"
                                android:layout_weight="70" />
                    </LinearLayout>
                    <LinearLayout
                            android:layout_width="match_parent"
                            android:layout_height="wrap_content"
                            android:orientation="horizontal">
                        <TextView
                                android:layout_width="0px"
                                android:layout_height="wrap_content"
                                android:layout_weight="30"
                                android:text="password : " />
                        <EditText
                                android:id="@+id/ed_password_ad"
                                android:layout_width="0px"
                                android:layout_height="wrap_content"
                                android:layout_weight="70" />
                    </LinearLayout>
                </LinearLayout>
            

code java pour un alert dialog avec une vue perso

                AlertDialog.Builder builder = new AlertDialog.Builder(context);
                builder.setTitle("my wonderful title");
                View view = LayoutInflater.from(context).inflate(R.layout.alert_dialog_layout,null);
                builder.setView(view);
                AlertDialog dialog = builder.show();
                

                EditText edLogin = view.findViewById(R.id.ed_login_ad);
            

                builder.setPositiveButton("Yes", new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialog, int which) {
                        AlertDialog alertDialog = (AlertDialog) dialog;
                        EditText edLogin = alertDialog.findViewById(R.id.ed_login_ad);
                    }
                });
            

                    view.setOnClickListener(new View.OnClickListener() {
                        @Override
                        public void onClick(View v) {
                            //action to do
                            v.setBackgroundColor(Color.GREEN);
                        }
                    });
                

                    view.setOnLongClickListener(new View.OnLongClickListener() {
                        @Override
                        public boolean onLongClick(View v) {
                            return true;
                        }
                    });
                

                    view.setOnFocusChangeListener(new View.OnFocusChangeListener() {
                        @Override
                        public void onFocusChange(View v, boolean hasFocus) {
                            if(hasFocus){
                                v.setBackgroundColor(Color.GREEN);
                            }else{
                                v.setBackgroundColor(Color.BLUE);
                            }
                        }
                    });
                

                    editText.addTextChangedListener(new TextWatcher() {
                        @Override
                        public void beforeTextChanged(CharSequence s, int start, int count, int after) {
                        }
                        @Override
                        public void onTextChanged(CharSequence s, int start, int before, int count) {
                        }
                        @Override
                        public void afterTextChanged(Editable s) {
                        }
                    });
                

                    radioButton.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {
                        @Override
                        public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
                        }
                    });
                

                    public class MainActivity extends AppCompactActivity {
                    ...
                    // exemple pour une activité, mais même approche pour une sous classe de View
                    @Override
                    public boolean onTouchEvent(MotionEvent event){
                    
                        int action = MotionEventCompat.getActionMasked(event);
                    
                        switch(action) {
                            case (MotionEvent.ACTION_DOWN) :
                                Log.d(DEBUG_TAG,"Action was DOWN");
                                return true;
                            case (MotionEvent.ACTION_MOVE) :
                                Log.d(DEBUG_TAG,"Action was MOVE");
                                return true;
                            case (MotionEvent.ACTION_UP) :
                                Log.d(DEBUG_TAG,"Action was UP");
                                return true;
                            case (MotionEvent.ACTION_OUTSIDE) :
                                Log.d(DEBUG_TAG,"Movement occurred outside bounds " +
                                        "of current screen element");
                                return true;
                            default :
                                return super.onTouchEvent(event);
                        }
                    }
                    
                    //exemple sur une sous-classe de View
                    View myView = findViewById(R.id.my_view);
                    myView.setOnTouchListener(new OnTouchListener() {
                        public boolean onTouch(View v, MotionEvent event) {
                            //action to do
                            return true;
                        }
                    });
                    
                

                    @Override
                    public boolean onTouchEvent(MotionEvent event) {
                        float xPosition = 0;
                        float yPosition = 0;
                        if(event.getActionMasked() == MotionEvent.ACTION_DOWN){
                            xPosition = event.getX();
                            yPosition = event.getY();
                        }
                        if(event.getActionMasked() == MotionEvent.ACTION_MOVE){
                            xPosition = event.getX();
                            yPosition = event.getY();
                        }
                        return super.onTouchEvent(event);
                    }
                

                    @Override
                    public boolean onTouchEvent(MotionEvent event) {
                        // get pointer index from the event object
                        int pointerIndex = event.getActionIndex();
                        // get pointer ID from pointerIndex
                        int pointerId = event.getPointerId(pointerIndex);
                        // get action
                        int maskedAction = event.getActionMasked();
                        switch (maskedAction) {
                            case MotionEvent.ACTION_DOWN:
                                Log.d(TAG, "index down: " + pointerId);
                                break;
                            case MotionEvent.ACTION_POINTER_DOWN: {
                                Log.d(TAG, "index down: " + pointerId);
                                break;
                            }
                            case MotionEvent.ACTION_MOVE: { // a pointer was moved
                                Log.d(TAG, "index move: " + pointerId);
                                break;
                            }
                            case MotionEvent.ACTION_UP:
                                Log.d(TAG, "index up: " + pointerId);
                
                                break;
                            case MotionEvent.ACTION_POINTER_UP:
                                Log.d(TAG, "index up: " + pointerId);
                                break;
                        }
                
                        return true;
                    }
                

                            public class EventActivity extends AppCompatActivity implements GestureDetector.OnGestureListener {
                                Context context;
                                @Override
                                protected void onCreate(Bundle savedInstanceState) {
                                    super.onCreate(savedInstanceState);
                                    context = this;
                                    setContentView(R.layout.activity_event);
                                }
                                @Override
                                public boolean onDown(MotionEvent e) {
                                    return false;
                                }
                                @Override
                                public void onShowPress(MotionEvent e) {
                                }
                                @Override
                                public boolean onSingleTapUp(MotionEvent e) {
                                    return false;
                                }
                                @Override
                                public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY) {
                                    return false;
                                }
                                @Override
                                public void onLongPress(MotionEvent e) {
                                }
                                @Override
                                public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY) {
                                    return false;
                                }
                            }
                        

                    public class EventActivity extends AppCompatActivity implements GestureDetector.OnGestureListener {
                        private String TAG = "debug-app";
                        GestureDetector gestureDetector;
                        Context context;
                        @Override
                        protected void onCreate(Bundle savedInstanceState) {
                            super.onCreate(savedInstanceState);
                            context = this;
                            setContentView(R.layout.activity_event);
                            gestureDetector = new GestureDetector(this,this);
                        }
                        @Override
                        public boolean onDown(MotionEvent e) {
                            return false;
                        }
                        @Override
                        public void onShowPress(MotionEvent e) {
                        }
                        @Override
                        public boolean onSingleTapUp(MotionEvent e) {
                            return false;
                        }
                        @Override
                        public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY) {
                            return false;
                        }
                        @Override
                        public void onLongPress(MotionEvent e) {
                        }
                        @Override
                        public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY) {
                            return false;
                        }
                    }
                

                    public class EventActivity extends AppCompatActivity implements GestureDetector.OnGestureListener {
                        private String TAG = "debug-app";
                        GestureDetector gestureDetector;
                        Context context;
                        @Override
                        protected void onCreate(Bundle savedInstanceState) {
                            super.onCreate(savedInstanceState);
                            context = this;
                            setContentView(R.layout.activity_event);
                            gestureDetector = new GestureDetector(this,this);
                        }
                        @Override
                        public boolean onTouchEvent(MotionEvent event) {
                            gestureDetector.onTouchEvent(event);
                            return true;
                        }
                        @Override
                        public boolean onDown(MotionEvent e) {
                            return false;
                        }
                        @Override
                        public void onShowPress(MotionEvent e) {
                        }
                        @Override
                        public boolean onSingleTapUp(MotionEvent e) {
                            return false;
                        }
                        @Override
                        public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY) {
                            return false;
                        }
                        @Override
                        public void onLongPress(MotionEvent e) {
                        }
                        @Override
                        public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY) {
                            return false;
                        }
                    }
                

                //si pas besoin de catégoriser les informations
                SharedPreferences sharedPreferences = PreferenceManager.getDefaultSharedPreferences(this);
                //si besoin de catégoriser
                SharedPreferences sharedPreferencesUser = context.getSharedPreferences("user", Context.MODE_PRIVATE);
            

                SharedPreferences sharedPreferences = PreferenceManager.getDefaultSharedPreferences(this);
                String guid = sharedPreferences.getString("id",null);
                int age = sharedPreferences.getInt("age",-1);
            

                SharedPreferences sharedPreferences = PreferenceManager.getDefaultSharedPreferences(this);
                SharedPreferences.Editor editor = sharedPreferences.edit();
                editor.putString("userName", "John Doe");
                editor.putFloat("xPosition", 42.56f);
                editor.putFloat("yPosition", 1056.89f);
                editor.apply();
            

                SharedPreferences sharedPreferences = PreferenceManager.getDefaultSharedPreferences(this);
                SharedPreferences.Editor editor = sharedPreferences.edit();
               
                //suppression par clef
                editor.remove("userName");
                editor.remove("id");
                editor.apply();
               
                //suppression total
                editor.clear();
                editor.apply();
            

            File file = new File(context.getFilesDir(), filename);
            

                String filename = "myFile.txt";
                String fileContents = "Hello world!";
                try (FileOutputStream fos = context.openFileOutput(filename, Context.MODE_PRIVATE)) {
                    fos.write(fileContents.toByteArray());
                }
            

                FileInputStream fileInputStream = context.openFileInput(fileName);
                InputStreamReader inputStreamReader =
                        new InputStreamReader(fileInputStream, StandardCharsets.UTF_8);
                StringBuilder stringBuilder = new StringBuilder();
                try (BufferedReader reader = new BufferedReader(inputStreamReader)) {
                    String line = reader.readLine();
                    while (line != null) {
                        stringBuilder.append(line).append('\n');
                        line = reader.readLine();
                    }
                } catch (IOException e) {
                    // Error occurred when opening raw file for reading.
                } finally {
                    String contents = stringBuilder.toString();
                }
            

                <uses-permission android:name="android.permission.MANAGE_EXTERNAL_STORAGE" />
            

                    File file = new File(Environment.getExternalStorageDirectory().getPath()+ File.separator+ "Android/data"+File.separator + getPackageName() + "/files/"+"myFile.txt" );
                

                CREATE TABLE etudiant (
                    id INTEGER PRIMARY KEY AUTOINCREMENT,
                    first_name TEXT,
                    last_name TEXT,
                    age
                );
            

                public class DataBaseHelper extends SQLiteOpenHelper {
                    public DataBaseHelper(@Nullable Context context, @Nullable String name, @Nullable SQLiteDatabase.CursorFactory factory, int version) {
                        super(context, name, factory, version);
                    }
                    @Override
                    public void onCreate(SQLiteDatabase db) {
                    }
                    @Override
                    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
                    }
                }
            

                @Override
                public void onCreate(SQLiteDatabase db) {
                    db.execSQL("CREATE TABLE etudiant (\n" +
                            "id INTEGER PRIMARY KEY AUTOINCREMENT," +
                            "first_name TEXT," +
                            "last_name TEXT," +
                            "age" +
                            ");");
                    db.execSQL("INSERT INTO etudiant ('first_name','last_name','age') values ('john','doe', 27), ('foo','bar',99);");
                }
                @Override
                public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
                    db.execSQL("DROP TABLE IF EXISTS etudiant");
                    onCreate(db);
                }
            

                public class ConnectionDB {
                    private static int version = 1;
                    private static String bnName = "myBd.db";
                    private static SQLiteDatabase bd = null;
                    private static DataBaseHelper helper;
                    
                    public static SQLiteDatabase getBd(Context context){
                        if(helper == null){
                            helper = new DataBaseHelper(context, bnName, null, version);
                        }
                        bd = helper.getWritableDatabase();
                        return bd;
                    }
                    public static void close(){
                        if(bd!= null &&  !bd.isOpen()){
                            bd.close();
                        }
                    }
                }
            

                    public class EtudiantManager {
                    
                        public static long add(Context context, Etudiant etudiantToAdd){
                            ContentValues contentValues = new ContentValues();
                            contentValues.put("first_name", etudiantToAdd.getFirstName());
                            contentValues.put("last_name", etudiantToAdd.getLastName());
                            contentValues.put("age", etudiantToAdd.getAge());
                            SQLiteDatabase bd = ConnectionDB.getBd(context); //on réutilise ConnctionDB ici
                            return bd.insert("etudiant", null, contentValues);
                        }
                    }
                

                public static void delete(Context context, int idEtudiant){
                    SQLiteDatabase bd = ConnectionDB.getBd(context);
                    bd.delete("etudiant","id = ?" , new String[]{String.valueOf(idEtudiant)});
                }
            

                public int delete (String table,
                                    String whereClause,
                                    String[] whereArgs)
            

                DELETE FROM etudiant WHERE id = ?
            

                DELETE FROM etudiant WHERE id = 7
            

                    DELETE FROM etudiant WHERE id = ? AND name LIKE ?
                

                    public static void update(Context context, Etudiant etudiantToUpdate) {
                        ContentValues contentValues = new ContentValues();
                        contentValues.put("first_name", etudiantToUpdate.getFirstName());
                        contentValues.put("age", etudiantToUpdate.getAge());
                        SQLiteDatabase bd = ConnectionDB.getBd(context);
                        long nbRowChange = bd.update("etudiant", contentValues, "id = ?", new String[]{String.valueOf(etudiantToUpdate.getId())});
                    }
                

                    public static ArrayList<Etudiant> getAll(Context context) {
                        SQLiteDatabase bd = ConnectionDB.getBd(context);
                        String query = "SELECT * FROM etudiant";
                        ArrayList<Etudiant> etudiants = null;
                        Cursor cursor = bd.rawQuery(query, null);
                        if (cursor.isBeforeFirst()) {
                            etudiants = new ArrayList<>();
                            while (cursor.moveToNext()) {
                                Etudiant etudiant = new Etudiant();
                                etudiant.setId(cursor.getInt(cursor.getColumnIndexOrThrow("id")));
                                etudiant.setFirstName(cursor.getString(cursor.getColumnIndexOrThrow("first_name")));
                                etudiant.setLastName(cursor.getString(cursor.getColumnIndexOrThrow("last_name")));
                                etudiant.setAge(cursor.getInt(cursor.getColumnIndexOrThrow("age")));
                                etudiants.add(etudiant);
                            }
                        }
                        return etudiants;
                    }
                

                public static ArrayList<Etudiant> getByAgeLimite(Context context, int ageLimite) {
                    SQLiteDatabase bd = ConnectionDB.getBd(context);
                    String query = "SELECT * FROM etudiant where age > ?";
                    ArrayList<Etudiant> etudiants = null;
                    Cursor cursor = bd.rawQuery(query, new String[]{String.valueOf(ageLimite)});
                    if (cursor.isBeforeFirst()) {
                        etudiants = new ArrayList<>();
                        while (cursor.moveToNext()) {
                            Etudiant etudiant = new Etudiant();
                            etudiant.setId(cursor.getInt(cursor.getColumnIndexOrThrow("id")));
                            etudiant.setFirstName(cursor.getString(cursor.getColumnIndexOrThrow("first_name")));
                            etudiant.setLastName(cursor.getString(cursor.getColumnIndexOrThrow("last_name")));
                            etudiant.setAge(cursor.getInt(cursor.getColumnIndexOrThrow("age")));
                            etudiants.add(etudiant);
                        }
                    }
                    return etudiants;
                }
                

                    SensorManager sensorManager = (SensorManager) getSystemService(Context.SENSOR_SERVICE);
                

                    List<Sensor> sensors = sensorManager.getSensorList(Sensor.TYPE_ALL);
                    for (Sensor sensor : sensors) {
                        Log.d("debug_app", "sensor: " + sensor.getName());
                        Log.d("debug_app", "sensor: " + sensor.getMinDelay());
                        Log.d("debug_app", "sensor: " + sensor.getVersion());
                        Log.d("debug_app", "sensor: " + sensor.getMaximumRange());
                    }
                

                    Sensor sensorLight = sensorManager.getDefaultSensor(Sensor.TYPE_LIGHT);
                    if(sensorLight != null){
                        // sensor existe
                    } else {
                        // prévenir l'utilisateur qu'on ne peut pas continuer
                    }
                

                SensorEventListener sensorEventListener = new SensorEventListener() {
                    @Override
                    public void onSensorChanged(SensorEvent event) {
                    }
                    @Override
                    public void onAccuracyChanged(Sensor sensor, int accuracy) {
                    }
                };
                

                    @Override
                    protected void onResume() {
                        super.onResume();
                        sensorManager.registerListener(sensorEventListener, sensorLight, SensorManager.SENSOR_DELAY_FASTEST);
                    }
                

                    @Override
                    protected void onPause() {
                        super.onPause();
                        sensorManager.unregisterListener(sensorEventListener,sensorLight);
                    }
                

                    public class SensorActivity extends AppCompatActivity {
                        TextView textView;
                        SensorManager sensorManager;
                        SensorEventListener sensorEventListener;
                        Sensor sensorLight;
                        @Override
                        protected void onCreate(Bundle savedInstanceState) {
                            super.onCreate(savedInstanceState);
                            setContentView(R.layout.activity_sensor);
                            textView = findViewById(R.id.text);
                            sensorManager = (SensorManager) getSystemService(Context.SENSOR_SERVICE);
                            sensorLight = sensorManager.getDefaultSensor(Sensor.TYPE_LIGHT);
                            sensorEventListener = new SensorEventListener() {
                                @Override
                                public void onSensorChanged(SensorEvent event) {
                                    float luxValue = event.values[0];
                                    textView.setText(String.valueOf(luxValue) + " lux");
                                }
                                @Override
                                public void onAccuracyChanged(Sensor sensor, int accuracy) {
                                }
                            };
                        }
                        @Override
                        protected void onResume() {
                            super.onResume();
                            sensorManager.registerListener(sensorEventListener, sensorLight, SensorManager.SENSOR_DELAY_FASTEST);
                        }
                        @Override
                        protected void onPause() {
                            super.onPause();
                            sensorManager.unregisterListener(sensorEventListener,sensorLight);
                        }
                    }
                

                    <uses-feature android:name="android.hardware.sensor.accelerometer"
                                  android:required="true" />
                

                    <?xml version="1.0" encoding="utf-8"?>
                    <manifest
                        xmlns:android="http://schemas.android.com/apk/res/android"
                        android:versionCode="1"
                        android:versionName="1.0">
                    
                        <uses-feature android:name="android.hardware.sensor.compass"
                            android:required="true" />
                    
                        <application
                            android:allowBackup="true"
                            android:icon="@mipmap/ic_launcher"
                            android:roundIcon="@mipmap/ic_launcher_round"
                            android:label="@string/app_name"
                            android:supportsRtl="true"
                            android:theme="@style/AppTheme">
                    
                            <activity android:name=".MainActivity">
                                <intent-filter>
                                    <action android:name="android.intent.action.MAIN" />
                                    <category android:name="android.intent.category.LAUNCHER" />
                                </intent-filter>
                            </activity>
                            <activity
                                android:name=".DisplayMessageActivity"
                                android:parentActivityName=".MainActivity" />
                        </application>
                    </manifest>
            

                plugins {
                    id 'com.android.application'
                }
                android {
                    namespace 'com.example.appname'
                    compileSdk 32
                    defaultConfig {
                        applicationId "com.example.appname"
                        minSdk 25
                        targetSdk 32
                        versionCode 1
                        versionName "1.0"
                        testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
                    }
                    buildTypes {
                        release {
                            minifyEnabled false
                            proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
                        }
                    }
                    compileOptions {
                        sourceCompatibility JavaVersion.VERSION_1_8
                        targetCompatibility JavaVersion.VERSION_1_8
                    }
                }
                dependencies {
                    implementation 'androidx.appcompat:appcompat:1.5.1'
                    implementation 'com.google.android.material:material:1.7.0'
                    implementation 'androidx.constraintlayout:constraintlayout:2.1.4'
                    testImplementation 'junit:junit:4.13.2'
                    androidTestImplementation 'androidx.test.ext:junit:1.1.3'
                    androidTestImplementation 'androidx.test.espresso:espresso-core:3.4.0'
                }
            

                    public class MainActivity extends AppCompatActivity {
                        @Override
                        protected void onCreate(Bundle savedInstanceState) {
                            super.onCreate(savedInstanceState);
                            setContentView(R.layout.activity_main);
                        }
                    }
                

                public class MainActivity extends AppCompatActivity {
                    private static final String TAG = "debug_app";
                    @Override
                    protected void onCreate(Bundle savedInstanceState) {
                        super.onCreate(savedInstanceState);
                        setContentView(R.layout.activity_main);
                        Log.d(TAG, "onCreate:");
                    }
                    @Override
                    protected void onStart() {
                        super.onStart();
                        Log.d(TAG, "onStart: ");
                    }
                    @Override
                    protected void onResume() {
                        super.onResume();
                        Log.d(TAG, "onResume: ");
                    }
                    @Override
                    protected void onPause() {
                        super.onPause();
                        Log.d(TAG, "onPause: ");
                    }
                    @Override
                    protected void onStop() {
                        super.onStop();
                        Log.d(TAG, "onStop: ");
                    }
                    @Override
                    protected void onDestroy() {
                        super.onDestroy();
                        Log.d(TAG, "onDestroy: ");
                    }
                }
            

                public class FirstActivity extends Activity {
                }
            

                public class FirstActivity extends AppCompatActivity {
                    @Override
                    protected void onCreate(@Nullable Bundle savedInstanceState) {
                        super.onCreate(savedInstanceState);
                        setContentView(R.layout.activity_first);
                    }
                }
            

                <application
                       ... >
                    <activity android:name=".FirstActivity"
                        android:exported="true">
                        <intent-filter>
                            <action android:name="android.intent.action.MAIN" />
                            <category android:name="android.intent.category.LAUNCHER" />
                        </intent-filter>
                    </activity>
                </application>
            

                <application
                       ... >
                    <activity android:name=".FirstActivity"
                        android:exported="true">
                        <intent-filter>
                            <action android:name="android.intent.action.MAIN" />
                            <category android:name="android.intent.category.LAUNCHER" />
                        </intent-filter>
                    </activity>
                    <activity android:name=".SecondActivité"
                        android:exported="false"/>
                </application>
            

                public class MainActivity extends AppCompatActivity {
                    Context context;
                    @Override
                    protected void onCreate(Bundle savedInstanceState) {
                        super.onCreate(savedInstanceState);
                        context = this; //don t forget this line, else you will have NullPointer
                        setContentView(R.layout.activity_main);
                    }
                }
            

                    android:id="@+id/my_id"
                

                    <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
                            xmlns:app="http://schemas.android.com/apk/res-auto"
                            xmlns:tools="http://schemas.android.com/tools"
                            android:layout_width="match_parent"
                            android:layout_height="match_parent"
                            android:orientation="vertical"
                            tools:context=".MainActivity">
                        <TextView
                                android:layout_width="match_parent"
                                android:layout_height="wrap_content"
                                android:text="Hello World!" />
                        <TextView
                                android:layout_width="wrap_content"
                                android:layout_height="wrap_content"
                                android:layout_gravity="right"
                                android:text="Hello World!" />
                        <TextView
                                android:layout_width="match_parent"
                                android:gravity="right"
                                android:layout_height="wrap_content"
                                android:text="Hello World!" />
                        <TextView
                                android:layout_width="wrap_content"
                                android:layout_height="wrap_content"
                                android:layout_gravity="center"
                                android:text="Hello World!" />
                    </LinearLayout>
                

                    <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
                            xmlns:app="http://schemas.android.com/apk/res-auto"
                            xmlns:tools="http://schemas.android.com/tools"
                            android:layout_width="match_parent"
                            android:layout_height="match_parent"
                            android:orientation="vertical"
                            tools:context=".MainActivity">
                        <Button
                                android:layout_width="match_parent"
                                android:layout_height="0dp"
                                android:layout_weight="40"
                                android:text="btn 1" />
                        <Button
                                android:layout_width="match_parent"
                                android:layout_height="0dp"
                                android:layout_weight="60"
                                android:text="btn 2" />
                    </LinearLayout>
                

                    <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
                            xmlns:app="http://schemas.android.com/apk/res-auto"
                            xmlns:tools="http://schemas.android.com/tools"
                            android:layout_width="match_parent"
                            android:layout_height="match_parent"
                            android:orientation="horizontal"
                            tools:context=".MainActivity">
                        <Button
                                android:layout_width="0dp"
                                android:layout_height="match_parent"
                                android:layout_weight="2"
                                android:text="btn 1" />
                        <Button
                                android:layout_width="0dp"
                                android:layout_height="match_parent"
                                android:layout_weight="5"
                                android:text="btn 2" />
                    </LinearLayout>
                

                    public class MainActivity extends AppCompatActivity {
                        Context context;
                        @Override
                        protected void onCreate(Bundle savedInstanceState) {
                            super.onCreate(savedInstanceState);
                            context = this;
                            //set UI width XML File
                            setContentView(R.layout.activity_main); //we give here reference of XML file
                            
                            //set view width Java File
                            LinearLayout container = new LinearLayout(context);
                            setContentView(container);
                        }
                    }
                

                        <?xml version="1.0" encoding="utf-8"?>
                        <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
                                xmlns:app="http://schemas.android.com/apk/res-auto"
                                xmlns:tools="http://schemas.android.com/tools"
                                android:layout_width="match_parent"
                                android:layout_height="match_parent"
                                android:orientation="vertical"
                                tools:context=".MainActivity">
                            <TextView
                                    android:layout_width="wrap_content"
                                    android:layout_height="wrap_content"
                                    android:text="Hello World!" />
                        </LinearLayout>
                

                    public class MainActivity extends AppCompatActivity {
                        @Override
                        protected void onCreate(Bundle savedInstanceState) {
                            super.onCreate(savedInstanceState);
                            setContentView(R.layout.activity_main);
                        }
                    }
                

                TextView tv = new TextView(this);
                LinearLayout.LayoutParams params = new LinearLayout.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.WRAP_CONTENT);
                tv.setLayoutParams(params);
                

                    public class MainActivity extends AppCompatActivity {
                        Context context;
                        @Override
                        protected void onCreate(Bundle savedInstanceState) {
                            super.onCreate(savedInstanceState);
                            context = this;
                            //create instance of linear layout
                            LinearLayout linearLayoutMain = new LinearLayout(context);
                            linearLayoutMain.setLayoutParams(new LinearLayout.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.MATCH_PARENT));
                            linearLayoutMain.setOrientation(LinearLayout.VERTICAL);
                            //add linearLayout as main container of activity
                            setContentView(linearLayoutMain);
                            //create textview
                            TextView textView = new TextView(context);
                            textView.setText("Hello World!");
                            textView.setLayoutParams(new LinearLayout.LayoutParams(ViewGroup.LayoutParams.WRAP_CONTENT, ViewGroup.LayoutParams.WRAP_CONTENT));
                            //set text view as child of linearlayout
                            linearLayoutMain.addView(textView);
                        }
                    }
                

                    <?xml version="1.0" encoding="utf-8"?>
                    <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
                            xmlns:app="http://schemas.android.com/apk/res-auto"
                            xmlns:tools="http://schemas.android.com/tools"
                            android:layout_width="match_parent"
                            android:layout_height="match_parent"
                            android:orientation="vertical"
                            tools:context=".MainActivity">
                        <TextView
                                android:id="@+id/text_view"
                                android:layout_width="wrap_content"
                                android:layout_height="wrap_content"
                                android:text="Hello World!" />
                    </LinearLayout>
                

                    public class MainActivity extends AppCompatActivity {
                        Context context;
                        @Override
                        protected void onCreate(Bundle savedInstanceState) {
                            super.onCreate(savedInstanceState);
                            context = this;
                            setContentView(R.layout.activity_main);
                            //access to textview
                            TextView textView = findViewById(R.id.text_view);
                            //change value of textview
                            textView.setText("New text to print");
                        }
                    }
                

                    <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
                            android:layout_width="match_parent"
                            android:layout_height="match_parent"
                            android:orientation="horizontal"
                            android:padding="5dp">
                        <TextView
                                android:layout_width="0dp"
                                android:layout_height="wrap_content"
                                android:layout_weight="10"
                                android:background="#f00"
                                android:gravity="center"
                                android:textSize="20dp"
                                android:textColor="#fff"
                                android:text="Left" />
                        <TextView
                                android:layout_width="0dp"
                                android:layout_height="wrap_content"
                                android:layout_weight="10"
                                android:background="#0f0"
                                android:gravity="center"
                                android:textSize="20dp"
                                android:textColor="#fff"
                                android:text="Right" />
                        <TextView
                                android:id="@+id/tv_view_number"
                                android:layout_width="0dp"
                                android:layout_height="wrap_content"
                                android:layout_weight="10"
                                android:background="#00f"
                                android:gravity="center"
                                android:textSize="20dp"
                                android:textColor="#fff"
                                android:text="No " />
                    </LinearLayout>
                

                    public class InflatorActivity extends AppCompatActivity {
                        Context context;
                        @Override
                        protected void onCreate(Bundle savedInstanceState) {
                            super.onCreate(savedInstanceState);
                            context = this;
                            LinearLayout llMain = new LinearLayout(context);
                            llMain.setOrientation(LinearLayout.VERTICAL);
                            setContentView(llMain);
                            for (int i = 0; i < 10; i++) {
                                //deserialization of view
                                LinearLayout linearLayoutSmallView = (LinearLayout) LayoutInflater.from(context).inflate(R.layout.small_view,null);
                                TextView textViewNumberView = linearLayoutSmallView.findViewById(R.id.tv_view_number);
                                textViewNumberView.setText("No : " + (i+1));
                                llMain.addView(linearLayoutSmallView);
                            }
                        }
                    }
                

                Intent intent = new Intent(ctx,ClassName.class);
                startActivity(intent);
            

                            Intent intent = new Intent(this, SecondeActivity.class);
                            intent.putExtra("name","user name");
                            intent.putExtra("id", "456-fesdf-464sdf");
                            intent.putExtra("year", 27);
                            startActivity(intent);
                        

                            Intent intent = getIntent();
                            String nameValue = intent.getStringExtra("name");
                            String idValue = intent.getStringExtra("id");
                            int yearValue =  intent.getIntExtra("year", -1);
                        

                ActivityResultLauncher<Intent> resultActivity = registerForActivityResult(
                        new ActivityResultContracts.StartActivityForResult(),
                        new ActivityResultCallback<ActivityResult>() {
                            @Override
                            public void onActivityResult(ActivityResult result) {
                                if (result.getResultCode() == RESULT_OK) {
                                    //do instruction when result
                                    Intent intent = result.getData();
                                    String dataString = intent.getStringExtra("dataKey");
                                }
                            }
                        }
                );
                Intent intent = new Intent(this, SecondeActivity.class);
                resultActivity.launch(intent);
            

                button.setOnClickListener(new View.OnClickListener() {
                    @Override
                    public void onClick(View v) {
                        Intent intent = new Intent();
                        intent.putExtra("dataKey","hello data"); //1
                        setResult(RESULT_OK, intent); //2
                        finish(); //3
                    }
                });
            

                    MyProject/
                        src/
                            MyActivity.java
                        res/
                            drawable/
                                graphic.png
                            layout/
                                main.xml
                                info.xml
                            mipmap/
                                icon.png
                            values/
                                strings.xml
                

                    public class R {
                        public static class layout{
                            public static final int activity_main = 0xabc123;
                            public static final int my_layout = 0xabc124;
                            public static final int other_layout = 0xabc125;
                        }
                        public static class drawable{
                            public static final int image1 = 0xbcd123;
                            public static final int image2 = 0xbcd124;
                            public static final int chat = 0xbcd125;
                        }
                        public static class string{
                            public static final int msg_welcom = 0xefa123;
                            public static final int app_name = 0xefa124;
                            public static final int msg_btn_send = 0xefa125;
                        }
                        public static class color{
                            public static final int color_texte = 0x456fa12;
                            public static final int color_btn = 0x456fa13;
                            public static final int color_border = 0x456fa14;
                            public static final int color_title = 0x456fa15;
                        }
                    }
                

                    Resources resources = context.getResources();
                    String stringRessource = resources.getString(R.string.key_ressource);
                    
                    //XXX resValue = resources.getXXX(id);
                

                    @[package:]type_ressource/nom_ressource
                

                    @+[package:]type/nom
                

                    <string name="dyn1">Hello %1$s, you have %2$d years</string>
                

                    Resources res = context.getResources();
                    String chaine = res.getString(R.string.dyn1, "durand", 32);
                

                    AssetManager assetManager = getAssets(); //into activity
                    AssetManager assetManager = context.getAssets(); // everywhere in application
                    try {
                        InputStream inputStream = assetManager.open("fileName");
                    } catch (IOException e) {
                        throw new RuntimeException(e);
                    }
                

                    InputStream inputStream = assetManager.open("fileName");
                    Drawable drawableImage = Drawable.createFromStream(inputStream, null);
                    Bitmap bitmapImage = BitmapFactory.decodeStream(inputStream);
                

                                <menu xmlns:android="http://schemas.android.com/apk/res/android"
                                    xmlns:app="http://schemas.android.com/apk/res-auto">
                                <item
                                        android:id="@+id/menu_play"
                                        android:icon="@android:drawable/ic_media_play"
                                        android:title="play"
                                        app:showAsAction="always" />
                                <item
                                        android:id="@+id/menu_stop"
                                        android:icon="@android:drawable/ic_media_stop"
                                        android:title="stop"
                                        app:showAsAction="always" />
                                <item
                                        android:id="@+id/menu_next"
                                        android:title="next"
                                        app:showAsAction="always" />
                                <item
                                        android:id="@+id/menu_pause"
                                        android:icon="@android:drawable/ic_media_pause"
                                        android:title="pause"
                                        app:showAsAction="ifRoom" />
                                <item
                                        android:id="@+id/menu_reset"
                                        android:title="reset"
                                        app:showAsAction="never" />
                            </menu>
                            

                @Override
                public boolean onCreateOptionsMenu(Menu menu) {
                    MenuInflater menuInflater = getMenuInflater();
                    menuInflater.inflate(R.menu.layout_menu, menu);
                    return true;
                }
            

                @Override
                public boolean onCreateOptionsMenu(Menu menu) {
                    int idItem = 1;        // exemple pour ajouter un item
                    int order = 1;
                    MenuItem menuItem = menu.add(0, idItem, order, "mon menu");
                    return true;
                }
            

                @Override
                public boolean onOptionsItemSelected(@NonNull MenuItem item) {
                    boolean retour = super.onOptionsItemSelected(item);
                    switch (item.getItemId()) {
                        case R.id.menu_play:
                            //action todo
                            retour = true;
                            break;
                        case R.id.menu_stop:
                            //action todo
                            retour = true;
                            break;
                        case R.id.menu_pause:
                            //action todo
                            retour = true;
                            break;
                        case R.id.menu_next:
                            //action todo
                            retour = true;
                            break;
                        case R.id.menu_reset:
                            //action todo
                            retour = true;
                            break;
                    }
                    return retour;
                }
            

                AlertDialog.Builder builder = new AlertDialog.Builder(context);
                builder.setTitle("my wonderful title");
                builder.setMessage("my beautiful Message to print ");
                AlertDialog dialog = builder.create();
                dialog.show();
                //or
                AlertDialog dialog = builder.show();
            

                AlertDialog.Builder builder = new AlertDialog.Builder(context);
                builder.setTitle("my wonderful title");
                builder.setMessage("my beautiful Message to print ");
                builder.setPositiveButton("Yes", new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialog, int which) {
                        //action if yes is select
                    }
                });
                builder.setNeutralButton("i don't know", new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialog, int which) {
                        //action if i don't know is select
                    }
                });
                builder.setPositiveButton("no", new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialog, int which) {
                        //action if no select
                    }
                });
                AlertDialog dialog = builder.show();
            

                String[] items = new String[]{"orange","blue","green"};
                AlertDialog.Builder builder = new AlertDialog.Builder(context);
                builder.setTitle("my wonderful title");
                builder.setItems(items, new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialog, int which) {
                        String value = items[which];//which = position of item select
                    }
                });
                AlertDialog dialog = builder.show();
            

                <string-array name="colors_list">
                    <item>orange</item>
                    <item>blue</item>
                    <item>green</item>
                </string-array>
            

                builder.setItems(R.array.colors_list, new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialog, int which) {
                        String[] items = getResources().getStringArray(R.array.colors_list); //pour récupérer les données depuis le répertoire Ressource
                        String value = items[which];//which = position of item select
                    }
                });
            

vue définie en xml

                <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
                        android:layout_width="match_parent"
                        android:layout_height="match_parent"
                        android:orientation="vertical">
                    <LinearLayout
                            android:layout_width="match_parent"
                            android:layout_height="wrap_content"
                            android:orientation="horizontal">
                        <TextView
                                android:layout_width="0px"
                                android:layout_height="wrap_content"
                                android:layout_weight="30"
                                android:text="login : " />
                        <EditText
                                android:id="@+id/ed_login_ad"
                                android:layout_width="0px"
                                android:layout_height="wrap_content"
                                android:layout_weight="70" />
                    </LinearLayout>
                    <LinearLayout
                            android:layout_width="match_parent"
                            android:layout_height="wrap_content"
                            android:orientation="horizontal">
                        <TextView
                                android:layout_width="0px"
                                android:layout_height="wrap_content"
                                android:layout_weight="30"
                                android:text="password : " />
                        <EditText
                                android:id="@+id/ed_password_ad"
                                android:layout_width="0px"
                                android:layout_height="wrap_content"
                                android:layout_weight="70" />
                    </LinearLayout>
                </LinearLayout>
            

code java pour un alert dialog avec une vue perso

                AlertDialog.Builder builder = new AlertDialog.Builder(context);
                builder.setTitle("my wonderful title");
                View view = LayoutInflater.from(context).inflate(R.layout.alert_dialog_layout,null);
                builder.setView(view);
                AlertDialog dialog = builder.show();
                

                EditText edLogin = view.findViewById(R.id.ed_login_ad);
            

                builder.setPositiveButton("Yes", new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialog, int which) {
                        AlertDialog alertDialog = (AlertDialog) dialog;
                        EditText edLogin = alertDialog.findViewById(R.id.ed_login_ad);
                    }
                });
            

                    view.setOnClickListener(new View.OnClickListener() {
                        @Override
                        public void onClick(View v) {
                            //action to do
                            v.setBackgroundColor(Color.GREEN);
                        }
                    });
                

                    view.setOnLongClickListener(new View.OnLongClickListener() {
                        @Override
                        public boolean onLongClick(View v) {
                            return true;
                        }
                    });
                

                    view.setOnFocusChangeListener(new View.OnFocusChangeListener() {
                        @Override
                        public void onFocusChange(View v, boolean hasFocus) {
                            if(hasFocus){
                                v.setBackgroundColor(Color.GREEN);
                            }else{
                                v.setBackgroundColor(Color.BLUE);
                            }
                        }
                    });
                

                    editText.addTextChangedListener(new TextWatcher() {
                        @Override
                        public void beforeTextChanged(CharSequence s, int start, int count, int after) {
                        }
                        @Override
                        public void onTextChanged(CharSequence s, int start, int before, int count) {
                        }
                        @Override
                        public void afterTextChanged(Editable s) {
                        }
                    });
                

                    radioButton.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {
                        @Override
                        public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
                        }
                    });
                

                    public class MainActivity extends AppCompactActivity {
                    ...
                    // exemple pour une activité, mais même approche pour une sous classe de View
                    @Override
                    public boolean onTouchEvent(MotionEvent event){
                    
                        int action = MotionEventCompat.getActionMasked(event);
                    
                        switch(action) {
                            case (MotionEvent.ACTION_DOWN) :
                                Log.d(DEBUG_TAG,"Action was DOWN");
                                return true;
                            case (MotionEvent.ACTION_MOVE) :
                                Log.d(DEBUG_TAG,"Action was MOVE");
                                return true;
                            case (MotionEvent.ACTION_UP) :
                                Log.d(DEBUG_TAG,"Action was UP");
                                return true;
                            case (MotionEvent.ACTION_OUTSIDE) :
                                Log.d(DEBUG_TAG,"Movement occurred outside bounds " +
                                        "of current screen element");
                                return true;
                            default :
                                return super.onTouchEvent(event);
                        }
                    }
                    
                    //exemple sur une sous-classe de View
                    View myView = findViewById(R.id.my_view);
                    myView.setOnTouchListener(new OnTouchListener() {
                        public boolean onTouch(View v, MotionEvent event) {
                            //action to do
                            return true;
                        }
                    });
                    
                

                    @Override
                    public boolean onTouchEvent(MotionEvent event) {
                        float xPosition = 0;
                        float yPosition = 0;
                        if(event.getActionMasked() == MotionEvent.ACTION_DOWN){
                            xPosition = event.getX();
                            yPosition = event.getY();
                        }
                        if(event.getActionMasked() == MotionEvent.ACTION_MOVE){
                            xPosition = event.getX();
                            yPosition = event.getY();
                        }
                        return super.onTouchEvent(event);
                    }
                

                    @Override
                    public boolean onTouchEvent(MotionEvent event) {
                        // get pointer index from the event object
                        int pointerIndex = event.getActionIndex();
                        // get pointer ID from pointerIndex
                        int pointerId = event.getPointerId(pointerIndex);
                        // get action
                        int maskedAction = event.getActionMasked();
                        switch (maskedAction) {
                            case MotionEvent.ACTION_DOWN:
                                Log.d(TAG, "index down: " + pointerId);
                                break;
                            case MotionEvent.ACTION_POINTER_DOWN: {
                                Log.d(TAG, "index down: " + pointerId);
                                break;
                            }
                            case MotionEvent.ACTION_MOVE: { // a pointer was moved
                                Log.d(TAG, "index move: " + pointerId);
                                break;
                            }
                            case MotionEvent.ACTION_UP:
                                Log.d(TAG, "index up: " + pointerId);
                
                                break;
                            case MotionEvent.ACTION_POINTER_UP:
                                Log.d(TAG, "index up: " + pointerId);
                                break;
                        }
                
                        return true;
                    }
                

                            public class EventActivity extends AppCompatActivity implements GestureDetector.OnGestureListener {
                                Context context;
                                @Override
                                protected void onCreate(Bundle savedInstanceState) {
                                    super.onCreate(savedInstanceState);
                                    context = this;
                                    setContentView(R.layout.activity_event);
                                }
                                @Override
                                public boolean onDown(MotionEvent e) {
                                    return false;
                                }
                                @Override
                                public void onShowPress(MotionEvent e) {
                                }
                                @Override
                                public boolean onSingleTapUp(MotionEvent e) {
                                    return false;
                                }
                                @Override
                                public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY) {
                                    return false;
                                }
                                @Override
                                public void onLongPress(MotionEvent e) {
                                }
                                @Override
                                public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY) {
                                    return false;
                                }
                            }
                        

                    public class EventActivity extends AppCompatActivity implements GestureDetector.OnGestureListener {
                        private String TAG = "debug-app";
                        GestureDetector gestureDetector;
                        Context context;
                        @Override
                        protected void onCreate(Bundle savedInstanceState) {
                            super.onCreate(savedInstanceState);
                            context = this;
                            setContentView(R.layout.activity_event);
                            gestureDetector = new GestureDetector(this,this);
                        }
                        @Override
                        public boolean onDown(MotionEvent e) {
                            return false;
                        }
                        @Override
                        public void onShowPress(MotionEvent e) {
                        }
                        @Override
                        public boolean onSingleTapUp(MotionEvent e) {
                            return false;
                        }
                        @Override
                        public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY) {
                            return false;
                        }
                        @Override
                        public void onLongPress(MotionEvent e) {
                        }
                        @Override
                        public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY) {
                            return false;
                        }
                    }
                

                    public class EventActivity extends AppCompatActivity implements GestureDetector.OnGestureListener {
                        private String TAG = "debug-app";
                        GestureDetector gestureDetector;
                        Context context;
                        @Override
                        protected void onCreate(Bundle savedInstanceState) {
                            super.onCreate(savedInstanceState);
                            context = this;
                            setContentView(R.layout.activity_event);
                            gestureDetector = new GestureDetector(this,this);
                        }
                        @Override
                        public boolean onTouchEvent(MotionEvent event) {
                            gestureDetector.onTouchEvent(event);
                            return true;
                        }
                        @Override
                        public boolean onDown(MotionEvent e) {
                            return false;
                        }
                        @Override
                        public void onShowPress(MotionEvent e) {
                        }
                        @Override
                        public boolean onSingleTapUp(MotionEvent e) {
                            return false;
                        }
                        @Override
                        public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY) {
                            return false;
                        }
                        @Override
                        public void onLongPress(MotionEvent e) {
                        }
                        @Override
                        public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY) {
                            return false;
                        }
                    }
                

                //si pas besoin de catégoriser les informations
                SharedPreferences sharedPreferences = PreferenceManager.getDefaultSharedPreferences(this);
                //si besoin de catégoriser
                SharedPreferences sharedPreferencesUser = context.getSharedPreferences("user", Context.MODE_PRIVATE);
            

                SharedPreferences sharedPreferences = PreferenceManager.getDefaultSharedPreferences(this);
                String guid = sharedPreferences.getString("id",null);
                int age = sharedPreferences.getInt("age",-1);
            

                SharedPreferences sharedPreferences = PreferenceManager.getDefaultSharedPreferences(this);
                SharedPreferences.Editor editor = sharedPreferences.edit();
                editor.putString("userName", "John Doe");
                editor.putFloat("xPosition", 42.56f);
                editor.putFloat("yPosition", 1056.89f);
                editor.apply();
            

                SharedPreferences sharedPreferences = PreferenceManager.getDefaultSharedPreferences(this);
                SharedPreferences.Editor editor = sharedPreferences.edit();
               
                //suppression par clef
                editor.remove("userName");
                editor.remove("id");
                editor.apply();
               
                //suppression total
                editor.clear();
                editor.apply();
            

            File file = new File(context.getFilesDir(), filename);
            

                String filename = "myFile.txt";
                String fileContents = "Hello world!";
                try (FileOutputStream fos = context.openFileOutput(filename, Context.MODE_PRIVATE)) {
                    fos.write(fileContents.toByteArray());
                }
            

                FileInputStream fileInputStream = context.openFileInput(fileName);
                InputStreamReader inputStreamReader =
                        new InputStreamReader(fileInputStream, StandardCharsets.UTF_8);
                StringBuilder stringBuilder = new StringBuilder();
                try (BufferedReader reader = new BufferedReader(inputStreamReader)) {
                    String line = reader.readLine();
                    while (line != null) {
                        stringBuilder.append(line).append('\n');
                        line = reader.readLine();
                    }
                } catch (IOException e) {
                    // Error occurred when opening raw file for reading.
                } finally {
                    String contents = stringBuilder.toString();
                }
            

                <uses-permission android:name="android.permission.MANAGE_EXTERNAL_STORAGE" />
            

                    File file = new File(Environment.getExternalStorageDirectory().getPath()+ File.separator+ "Android/data"+File.separator + getPackageName() + "/files/"+"myFile.txt" );
                

                CREATE TABLE etudiant (
                    id INTEGER PRIMARY KEY AUTOINCREMENT,
                    first_name TEXT,
                    last_name TEXT,
                    age
                );
            

                public class DataBaseHelper extends SQLiteOpenHelper {
                    public DataBaseHelper(@Nullable Context context, @Nullable String name, @Nullable SQLiteDatabase.CursorFactory factory, int version) {
                        super(context, name, factory, version);
                    }
                    @Override
                    public void onCreate(SQLiteDatabase db) {
                    }
                    @Override
                    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
                    }
                }
            

                @Override
                public void onCreate(SQLiteDatabase db) {
                    db.execSQL("CREATE TABLE etudiant (\n" +
                            "id INTEGER PRIMARY KEY AUTOINCREMENT," +
                            "first_name TEXT," +
                            "last_name TEXT," +
                            "age" +
                            ");");
                    db.execSQL("INSERT INTO etudiant ('first_name','last_name','age') values ('john','doe', 27), ('foo','bar',99);");
                }
                @Override
                public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
                    db.execSQL("DROP TABLE IF EXISTS etudiant");
                    onCreate(db);
                }
            

                public class ConnectionDB {
                    private static int version = 1;
                    private static String bnName = "myBd.db";
                    private static SQLiteDatabase bd = null;
                    private static DataBaseHelper helper;
                    
                    public static SQLiteDatabase getBd(Context context){
                        if(helper == null){
                            helper = new DataBaseHelper(context, bnName, null, version);
                        }
                        bd = helper.getWritableDatabase();
                        return bd;
                    }
                    public static void close(){
                        if(bd!= null &&  !bd.isOpen()){
                            bd.close();
                        }
                    }
                }
            

                    public class EtudiantManager {
                    
                        public static long add(Context context, Etudiant etudiantToAdd){
                            ContentValues contentValues = new ContentValues();
                            contentValues.put("first_name", etudiantToAdd.getFirstName());
                            contentValues.put("last_name", etudiantToAdd.getLastName());
                            contentValues.put("age", etudiantToAdd.getAge());
                            SQLiteDatabase bd = ConnectionDB.getBd(context); //on réutilise ConnctionDB ici
                            return bd.insert("etudiant", null, contentValues);
                        }
                    }
                

                public static void delete(Context context, int idEtudiant){
                    SQLiteDatabase bd = ConnectionDB.getBd(context);
                    bd.delete("etudiant","id = ?" , new String[]{String.valueOf(idEtudiant)});
                }
            

                public int delete (String table,
                                    String whereClause,
                                    String[] whereArgs)
            

                DELETE FROM etudiant WHERE id = ?
            

                DELETE FROM etudiant WHERE id = 7
            

                    DELETE FROM etudiant WHERE id = ? AND name LIKE ?
                

                    public static void update(Context context, Etudiant etudiantToUpdate) {
                        ContentValues contentValues = new ContentValues();
                        contentValues.put("first_name", etudiantToUpdate.getFirstName());
                        contentValues.put("age", etudiantToUpdate.getAge());
                        SQLiteDatabase bd = ConnectionDB.getBd(context);
                        long nbRowChange = bd.update("etudiant", contentValues, "id = ?", new String[]{String.valueOf(etudiantToUpdate.getId())});
                    }
                

                    public static ArrayList<Etudiant> getAll(Context context) {
                        SQLiteDatabase bd = ConnectionDB.getBd(context);
                        String query = "SELECT * FROM etudiant";
                        ArrayList<Etudiant> etudiants = null;
                        Cursor cursor = bd.rawQuery(query, null);
                        if (cursor.isBeforeFirst()) {
                            etudiants = new ArrayList<>();
                            while (cursor.moveToNext()) {
                                Etudiant etudiant = new Etudiant();
                                etudiant.setId(cursor.getInt(cursor.getColumnIndexOrThrow("id")));
                                etudiant.setFirstName(cursor.getString(cursor.getColumnIndexOrThrow("first_name")));
                                etudiant.setLastName(cursor.getString(cursor.getColumnIndexOrThrow("last_name")));
                                etudiant.setAge(cursor.getInt(cursor.getColumnIndexOrThrow("age")));
                                etudiants.add(etudiant);
                            }
                        }
                        return etudiants;
                    }
                

                public static ArrayList<Etudiant> getByAgeLimite(Context context, int ageLimite) {
                    SQLiteDatabase bd = ConnectionDB.getBd(context);
                    String query = "SELECT * FROM etudiant where age > ?";
                    ArrayList<Etudiant> etudiants = null;
                    Cursor cursor = bd.rawQuery(query, new String[]{String.valueOf(ageLimite)});
                    if (cursor.isBeforeFirst()) {
                        etudiants = new ArrayList<>();
                        while (cursor.moveToNext()) {
                            Etudiant etudiant = new Etudiant();
                            etudiant.setId(cursor.getInt(cursor.getColumnIndexOrThrow("id")));
                            etudiant.setFirstName(cursor.getString(cursor.getColumnIndexOrThrow("first_name")));
                            etudiant.setLastName(cursor.getString(cursor.getColumnIndexOrThrow("last_name")));
                            etudiant.setAge(cursor.getInt(cursor.getColumnIndexOrThrow("age")));
                            etudiants.add(etudiant);
                        }
                    }
                    return etudiants;
                }
                

                    SensorManager sensorManager = (SensorManager) getSystemService(Context.SENSOR_SERVICE);
                

                    List<Sensor> sensors = sensorManager.getSensorList(Sensor.TYPE_ALL);
                    for (Sensor sensor : sensors) {
                        Log.d("debug_app", "sensor: " + sensor.getName());
                        Log.d("debug_app", "sensor: " + sensor.getMinDelay());
                        Log.d("debug_app", "sensor: " + sensor.getVersion());
                        Log.d("debug_app", "sensor: " + sensor.getMaximumRange());
                    }
                

                    Sensor sensorLight = sensorManager.getDefaultSensor(Sensor.TYPE_LIGHT);
                    if(sensorLight != null){
                        // sensor existe
                    } else {
                        // prévenir l'utilisateur qu'on ne peut pas continuer
                    }
                

                SensorEventListener sensorEventListener = new SensorEventListener() {
                    @Override
                    public void onSensorChanged(SensorEvent event) {
                    }
                    @Override
                    public void onAccuracyChanged(Sensor sensor, int accuracy) {
                    }
                };
                

                    @Override
                    protected void onResume() {
                        super.onResume();
                        sensorManager.registerListener(sensorEventListener, sensorLight, SensorManager.SENSOR_DELAY_FASTEST);
                    }
                

                    @Override
                    protected void onPause() {
                        super.onPause();
                        sensorManager.unregisterListener(sensorEventListener,sensorLight);
                    }
                

                    public class SensorActivity extends AppCompatActivity {
                        TextView textView;
                        SensorManager sensorManager;
                        SensorEventListener sensorEventListener;
                        Sensor sensorLight;
                        @Override
                        protected void onCreate(Bundle savedInstanceState) {
                            super.onCreate(savedInstanceState);
                            setContentView(R.layout.activity_sensor);
                            textView = findViewById(R.id.text);
                            sensorManager = (SensorManager) getSystemService(Context.SENSOR_SERVICE);
                            sensorLight = sensorManager.getDefaultSensor(Sensor.TYPE_LIGHT);
                            sensorEventListener = new SensorEventListener() {
                                @Override
                                public void onSensorChanged(SensorEvent event) {
                                    float luxValue = event.values[0];
                                    textView.setText(String.valueOf(luxValue) + " lux");
                                }
                                @Override
                                public void onAccuracyChanged(Sensor sensor, int accuracy) {
                                }
                            };
                        }
                        @Override
                        protected void onResume() {
                            super.onResume();
                            sensorManager.registerListener(sensorEventListener, sensorLight, SensorManager.SENSOR_DELAY_FASTEST);
                        }
                        @Override
                        protected void onPause() {
                            super.onPause();
                            sensorManager.unregisterListener(sensorEventListener,sensorLight);
                        }
                    }
                

                    <uses-feature android:name="android.hardware.sensor.accelerometer"
                                  android:required="true" />
                

                    <?xml version="1.0" encoding="utf-8"?>
                    <manifest
                        xmlns:android="http://schemas.android.com/apk/res/android"
                        android:versionCode="1"
                        android:versionName="1.0">
                    
                        <uses-feature android:name="android.hardware.sensor.compass"
                            android:required="true" />
                    
                        <application
                            android:allowBackup="true"
                            android:icon="@mipmap/ic_launcher"
                            android:roundIcon="@mipmap/ic_launcher_round"
                            android:label="@string/app_name"
                            android:supportsRtl="true"
                            android:theme="@style/AppTheme">
                    
                            <activity android:name=".MainActivity">
                                <intent-filter>
                                    <action android:name="android.intent.action.MAIN" />
                                    <category android:name="android.intent.category.LAUNCHER" />
                                </intent-filter>
                            </activity>
                            <activity
                                android:name=".DisplayMessageActivity"
                                android:parentActivityName=".MainActivity" />
                        </application>
                    </manifest>
            

                plugins {
                    id 'com.android.application'
                }
                android {
                    namespace 'com.example.appname'
                    compileSdk 32
                    defaultConfig {
                        applicationId "com.example.appname"
                        minSdk 25
                        targetSdk 32
                        versionCode 1
                        versionName "1.0"
                        testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
                    }
                    buildTypes {
                        release {
                            minifyEnabled false
                            proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
                        }
                    }
                    compileOptions {
                        sourceCompatibility JavaVersion.VERSION_1_8
                        targetCompatibility JavaVersion.VERSION_1_8
                    }
                }
                dependencies {
                    implementation 'androidx.appcompat:appcompat:1.5.1'
                    implementation 'com.google.android.material:material:1.7.0'
                    implementation 'androidx.constraintlayout:constraintlayout:2.1.4'
                    testImplementation 'junit:junit:4.13.2'
                    androidTestImplementation 'androidx.test.ext:junit:1.1.3'
                    androidTestImplementation 'androidx.test.espresso:espresso-core:3.4.0'
                }
            

                    public class MainActivity extends AppCompatActivity {
                        @Override
                        protected void onCreate(Bundle savedInstanceState) {
                            super.onCreate(savedInstanceState);
                            setContentView(R.layout.activity_main);
                        }
                    }
                

                public class MainActivity extends AppCompatActivity {
                    private static final String TAG = "debug_app";
                    @Override
                    protected void onCreate(Bundle savedInstanceState) {
                        super.onCreate(savedInstanceState);
                        setContentView(R.layout.activity_main);
                        Log.d(TAG, "onCreate:");
                    }
                    @Override
                    protected void onStart() {
                        super.onStart();
                        Log.d(TAG, "onStart: ");
                    }
                    @Override
                    protected void onResume() {
                        super.onResume();
                        Log.d(TAG, "onResume: ");
                    }
                    @Override
                    protected void onPause() {
                        super.onPause();
                        Log.d(TAG, "onPause: ");
                    }
                    @Override
                    protected void onStop() {
                        super.onStop();
                        Log.d(TAG, "onStop: ");
                    }
                    @Override
                    protected void onDestroy() {
                        super.onDestroy();
                        Log.d(TAG, "onDestroy: ");
                    }
                }
            

                public class FirstActivity extends Activity {
                }
            

                public class FirstActivity extends AppCompatActivity {
                    @Override
                    protected void onCreate(@Nullable Bundle savedInstanceState) {
                        super.onCreate(savedInstanceState);
                        setContentView(R.layout.activity_first);
                    }
                }
            

                <application
                       ... >
                    <activity android:name=".FirstActivity"
                        android:exported="true">
                        <intent-filter>
                            <action android:name="android.intent.action.MAIN" />
                            <category android:name="android.intent.category.LAUNCHER" />
                        </intent-filter>
                    </activity>
                </application>
            

                <application
                       ... >
                    <activity android:name=".FirstActivity"
                        android:exported="true">
                        <intent-filter>
                            <action android:name="android.intent.action.MAIN" />
                            <category android:name="android.intent.category.LAUNCHER" />
                        </intent-filter>
                    </activity>
                    <activity android:name=".SecondActivité"
                        android:exported="false"/>
                </application>
            

                public class MainActivity extends AppCompatActivity {
                    Context context;
                    @Override
                    protected void onCreate(Bundle savedInstanceState) {
                        super.onCreate(savedInstanceState);
                        context = this; //don t forget this line, else you will have NullPointer
                        setContentView(R.layout.activity_main);
                    }
                }
            

                    android:id="@+id/my_id"
                

                    <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
                            xmlns:app="http://schemas.android.com/apk/res-auto"
                            xmlns:tools="http://schemas.android.com/tools"
                            android:layout_width="match_parent"
                            android:layout_height="match_parent"
                            android:orientation="vertical"
                            tools:context=".MainActivity">
                        <TextView
                                android:layout_width="match_parent"
                                android:layout_height="wrap_content"
                                android:text="Hello World!" />
                        <TextView
                                android:layout_width="wrap_content"
                                android:layout_height="wrap_content"
                                android:layout_gravity="right"
                                android:text="Hello World!" />
                        <TextView
                                android:layout_width="match_parent"
                                android:gravity="right"
                                android:layout_height="wrap_content"
                                android:text="Hello World!" />
                        <TextView
                                android:layout_width="wrap_content"
                                android:layout_height="wrap_content"
                                android:layout_gravity="center"
                                android:text="Hello World!" />
                    </LinearLayout>
                

                    <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
                            xmlns:app="http://schemas.android.com/apk/res-auto"
                            xmlns:tools="http://schemas.android.com/tools"
                            android:layout_width="match_parent"
                            android:layout_height="match_parent"
                            android:orientation="vertical"
                            tools:context=".MainActivity">
                        <Button
                                android:layout_width="match_parent"
                                android:layout_height="0dp"
                                android:layout_weight="40"
                                android:text="btn 1" />
                        <Button
                                android:layout_width="match_parent"
                                android:layout_height="0dp"
                                android:layout_weight="60"
                                android:text="btn 2" />
                    </LinearLayout>
                

                    <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
                            xmlns:app="http://schemas.android.com/apk/res-auto"
                            xmlns:tools="http://schemas.android.com/tools"
                            android:layout_width="match_parent"
                            android:layout_height="match_parent"
                            android:orientation="horizontal"
                            tools:context=".MainActivity">
                        <Button
                                android:layout_width="0dp"
                                android:layout_height="match_parent"
                                android:layout_weight="2"
                                android:text="btn 1" />
                        <Button
                                android:layout_width="0dp"
                                android:layout_height="match_parent"
                                android:layout_weight="5"
                                android:text="btn 2" />
                    </LinearLayout>